The coagulation and liquefaction of semen is a physiological mechanism of self-protection in mammals and primates during natural reproduction, and human semen retains this feature. During sexual intercourse, semen is quickly solidified in a gel-like form and is guaranteed to remain in the vagina of the woman (female). The semen then begins to liquefy and the spermatozoa appear to move actively, facilitating further sperm penetration and fertilization. As we can see, after mating in some rodents, the vaginal opening of the female forms a pubic plug due to the solidification of the semen, which acts as a plug. Similarly, in primates such as monkeys or gorillas, the expelled semen coagulates instantly, and even after a certain period of liquefaction, there is still a significant portion of the very solid gelatinous material that is difficult to liquefy completely. This physiological phenomenon seems to have become less important in humans as the species has evolved. The vast majority of human semen is completely liquefied within a few minutes or tens of minutes after being expelled from the body. Married couples have experienced that shortly after intercourse, a portion of semen automatically exits the body from the vagina with a change in position. Disorders of human semen liquefaction are considered to be one of the causes of male fertility. Indeed, microscopic observation of sperm movement in unliquefied semen is extremely weak or even immobile. Theoretically, any factor that impedes sperm movement reduces male fertility, so poor liquefaction seems to be a logical cause of infertility. However, according to a systematic medical literature search, there is a lot of literature on semen liquefaction in male infertility patients, although it is mostly found in domestic articles and is mostly focused on reports of the efficacy of Chinese medicine in treating (poorly liquefied) infertility. However, the basic premise of whether there is an inevitable relationship between poor liquefaction and reduced male fertility has not been sufficiently documented by evidence-based medicine (an accepted discipline in modern medicine that objectively assesses the scientific basis of disease etiology, diagnosis and efficacy). The determination of semen liquefaction is one of the components of routine semen analysis. The current common method is to observe the disappearance of gel-like material in semen in vitro according to the naked eye, and a small amount of jelly-like material the size of a grain of rice can be seen after normal semen liquefaction. According to WHO standards, abnormal semen liquefaction is defined as a complete liquefaction of semen more than 60 minutes after ejaculation. Semen analysis is performed in vitro under an essentially static simulated condition, but the possible effects on semen liquefaction of the temperature, pH, and muscle stretching of the vaginal environment after semen enters the vagina during sexual intercourse cannot be simulated in vitro. Therefore, there is no accepted objective method for quantitative analysis to date. In our clinical work, we often encounter a high percentage of delayed or non-liquefied semen reports from hospitals, as well as a significant number of poorly liquefied tests with very good sperm motility. The latter is clearly illogical, or at least the etiological diagnosis of poor semen liquefaction in the latter case of infertility is hasty. We reckon that these tests failed to distinguish abnormal semen liquefaction from abnormal viscosity and misclassified increased viscosity as liquefaction disorder (this may be related to the lack of standardization of semen analysis in the laboratory departments of many general hospitals). It is clear that semen liquefaction disorders and hyperviscosity are physiological states of different nature. The former refers to semen that is not liquefied in a gel state, while the latter reflects the viscosity of semen that is already in a liquid state. Therefore, if the semen analysis you receive at the time of your visit reports impaired liquefaction and normal or near-normal sperm motility, it is time to wonder if the true cause of infertility is due to “liquefaction”. There is a lack of evidence as to whether liquefaction is a common cause of infertility in humans, as there are many causes of infertility and not all of them can be effectively detected (due to the limitations of current medical technology).