Psoriasis, commonly known as psoriasis, is a common and multifaceted disease in dermatology. Patients most often present with recurrent red patches of skin covered with silvery-white scales. The area can range from the size of a pinpoint to a large area that spreads throughout the body. Since psoriasis is a chronic disease, it tends to recur and there is no cure, so patients are often very distressed. The treatment of psoriasis has also become an important topic of dermatological science in ancient and modern times. People have done quite a lot of exploration and research in this area, and a variety of effective treatment means have been summarized in modern times. Among them, the most commonly applied are a variety of topical preparations, such as hormonal drugs, retinoids, vitamin D derivatives, as well as tar, enlin, keratin enabling agents and emollients. For more severe cases oral medications are also used, including immunosuppressants, retinoids, etc. In addition to medications, there are also physical means to effectively treat psoriasis, including phototherapy, hydrotherapy, and climate therapy. This article focuses on the most effective of these, and currently the most widely used, ultraviolet light therapy. In general, UV light therapy has the following advantages in the treatment of psoriasis: 1. A large number of clinical data show that PUVA and narrow-spectrum UVB methods have very certain efficacy, and most psoriasis patients can achieve satisfactory results after appropriate phototherapy treatment. 2.The relevant equipment is perfect and can be adapted to various disease situations. Due to the development of science and technology, we have a variety of artificial ultraviolet light sources and a variety of different specifications of ultraviolet light therapy equipment. For different patients, different parts of the disease can choose a variety of irradiation equipment, from local patients to systemic patients, and even individual parts, can use the corresponding equipment for treatment. 3, treatment is fast and convenient, without hospitalization. Phototherapy is generally carried out in the day treatment center of the hospital’s dermatology department, and patients can flexibly arrange the treatment time according to their own situation and the doctor’s advice, which only takes a few minutes to a few minutes each time. Thus, it has less impact on normal life and work. 4, good safety, no rebound after stopping treatment. As phototherapy methods are carried out for a longer and longer time, more and more experience, its safety is being widely confirmed. Now the dermatological community is recognized as a safer treatment method of phototherapy (see below for side effects of phototherapy treatment). Most patients can obtain a longer period of remission after treatment. Patients can choose the appropriate maintenance therapy to reduce and delay recurrence after treatment is completed. 5. Treatment is not expensive. At present, the core components of phototherapy equipment can not be produced in China, so the price of phototherapy-related equipment is still relatively expensive. But the consumption of equipment components in the treatment process is less, so the cost of phototherapy treatment is not very high, taking into account the efficiency of its treatment, relative to other therapies, the author believes that phototherapy is a more economical treatment method. Due to the above characteristics of UV light therapy, we recommend many patients to receive light therapy treatment. However, there are still some problems in the treatment of psoriasis by phototherapy, which cannot be ignored: 1. The pathogenesis of psoriasis is still not known to science, and further research is needed on the mechanism of phototherapy for psoriasis, and phototherapy cannot fundamentally solve the problem of psoriasis recurrence. Be sure to achieve reasonable application. 2. There are generally side effects associated with phototherapy methods, including acute erythema and sunburn reactions; medium- and long-term treatment will result in skin dryness, tanning, sun spots and photodamaged skin aging; long-term cumulative irradiation will increase the risk of skin tumor occurrence. For individual patients, it is important to consider whether there are relevant relative and absolute contraindications to phototherapy. For example, PUVA therapy is contraindicated in pregnant women, various light therapies are contraindicated in patients with pigmented dry skin disease, patients taking certain photosensitizing medications, patients with skin tumors, and children may be relative contraindications to certain light therapies. All of the above risks require that phototherapy must be performed under the guidance of a specialized dermatologist, who will study the appropriate treatment plan according to the patient’s actual condition and the indications. Avoid acute adverse reactions, reduce the cumulative dose under the premise of ensuring appropriate efficacy, and reduce long-term adverse reactions. 3.At present, the treatment of psoriasis by phototherapy mainly relies on the summary of clinical experience, and no strict treatment specification has been formulated. The evaluation of the efficacy of phototherapy and the examination of long-term safety are still in progress. This requires that both doctors and patients should try to understand the relevant knowledge and operate meticulously. It should not be carried out blindly and used indiscriminately. 4.Psoriasis is a chronic skin disease affected by a variety of factors and requires comprehensive treatment. Therefore, while applying phototherapy, it should also reasonably cooperate with other effective treatment means and auxiliary treatment means. This can improve the efficacy, reduce the adverse effects of phototherapy, reduce the pain of patients and improve the quality of life. Various treatment methods, including ultraviolet light therapy, have been developed through scientific research. Such research is still underway today with the rapid development of medical technology. It is believed that through the development of new methods and the rational use of existing means, and the improvement of the level of medical service guarantee, psoriasis, a disease that has long plagued patients and the dermatological science community, can be well resolved.