Most organisms on Earth generally live according to a circadian rhythm that is determined by the Earth’s light cycle. Plants, animals, and even single-celled organisms exhibit circadian rhythmicity in metabolic activity, locomotion, feeding, and a variety of other activities. We have studied the importance of the effect of light cycle on human biological clock in blind volunteers. One-third of the subjects were in a natural environment; one-third were in an unnatural environment, but the cycle of that environment was still 24 hours; and another third were in an environment with a cycle of more than 24 hours. The first symptom of circadian rhythm disorder is that people cannot fall asleep when they should, but once they fall asleep, the quality of sleep is no different from normal, only the sleep time will be different. The reason for this is that the circadian rhythm is disrupted, but the biological clock is not able to adjust to the new geophysical environment in time. This disruption of the wake-sleep cycle can be divided into two main categories, namely primary disorders due to the dysfunction of the human biological clock itself and secondary disorders due to environmental factors that affect the function of the biological clock. Wake-sleep disorders occurring in cases such as jet lag syndrome and shift work are secondary disorders, and the cause of these disorders can be quickly determined by a simple consultation. In contrast, primary wake-sleep disorders are more difficult to diagnose because they present with many other types of sleep disorders, such as hypersomnia, insomnia, sedative-hypnotic drug or stimulant addiction, and other psychiatric symptoms. Until now, only scientific researchers have shown interest in circadian rhythm disorders because we have not yet found an effective treatment. Happily, however, a breakthrough has been made, and we now have more accurate diagnoses and more effective treatments to help those who suffer from chronic circadian rhythm disorders. The most prominent treatments are now chronotherapy and phototherapy. In addition, some new drugs have also emerged. The so-called chronotherapy is to let the patient in a period of “free time” in accordance with the established sleep schedule to arrange sleep. The patient has to go to sleep a few hours earlier or later each day, and the sleep schedule has to be strictly followed until finally the sleep time can be adjusted to the predetermined point in time, and at the same time, the predetermined sleep time can also be guaranteed. Using this therapy requires the patient to undergo continuous treatment for a period of time (several days) and the treatment room must be sufficiently quiet and dark, otherwise the treatment cannot be performed during the day. The so-called phototherapy is a light therapy in which the patient is placed in a lighted environment and the light therapy is performed according to a set time and cycle (the cycle is designed according to the human wake-sleep rhythm), which is more effective in regulating the patient’s biological clock. It is very suitable for the treatment of patients with circadian rhythm disorders. The duration and period of light therapy treatment varies depending on the individual patient. During the treatment, the patient sits at a distance from the light source, which ensures that the patient receives an amount of light exposure of 2500 lux (lux). The ability of light therapy to regulate the body’s circadian rhythm depends on the intensity and wavelength of the light, the duration of the light exposure, and the length of the exposure. After phototherapy treatment, the treatment must be maintained once the desired goal has been achieved, such as the patient being able to get enough sleep. There is still much about light therapy that we do not understand in our clinical work, and we need to continue to research and explore in order to better grasp the various variables of this therapy so that light therapy can help patients to the maximum extent possible. Patients with Delayed sleep syndrome (DSPS) exhibit a later-than-average sleep and a later-than-average rise. They are unable to fall asleep at the normal bedtime. We can interpret this disorder as suffering from insomnia when it is time to fall asleep and hypersomnia when it is time to wake up. Sleep phase lapse syndrome is the most common type of primary circadian rhythm disorder, and patients may suffer from it partly because of the increasing night work and life, etc. This is evidenced by the fact that college students are accustomed to going to bed after 2:00 a.m., but are unable to get up at 8:00 a.m. when it is time to go to class. Even if they do get up in the morning, they will still be napping in class. However, if these students are allowed to sleep until they wake up naturally, they will be so refreshed that they will never nod off again throughout the day. In the face of such patients, a combination of chronotherapy, light therapy and drug therapy may work. But unfortunately, the treatment cannot be interrupted, once the treatment is interrupted, the patient’s biological clock will “slow down” again. Patients with advanced sleep-phase syndrome (ASPS) are just the opposite of those with sleep-phase shift syndrome, they go to sleep earlier and wake up earlier than the average person, falling asleep and waking up hours earlier than the average person. These patients act as if they suffer from hypersomnia when everyone is still asleep, and as if they suffer from insomnia when everyone is already asleep. These patients were unable to do much activity during the night because they had to sleep. In turn, their waking performance in the early morning hours is often misdiagnosed as a sign of depression. Giving these patients a certain amount of time at night with light therapy helps delay their biological clocks. Other less prevalent circadian rhythm disorders include non-24-hour wake-sleep patterns and irregular wake-sleep patterns. We have now identified genes associated with the aforementioned sleep phase lapse syndrome and sleep phase advance syndrome, suggesting that both disorders also have a predisposition to be inherited. We call those drugs that regulate the body’s biological rhythms chronobiotics. One of the most promising drugs is melatonin. Melatonin is secreted by the human pineal gland and its secretion is regulated by wakefulness-sleep and correlates with the circadian rhythm of corticosteroid secretion. The secretion of melatonin can be used to indirectly understand how the body sleeps. It is likely that melatonin plays a very important role in the control of human biological rhythms. This is because there is evidence that the use of exogenous melatonin can alter the body’s biological rhythms. Circadian rhythm disorders are very common and can have a significant impact on our lives, studies and work, hence the urgent need for efficacious chronopharmacological drugs.