The main male factor in pregnancy is semen quality, and semen routine is widely used as an easy, quick and sensitive test. It is well known that repeated routine semen tests for azoospermia may lead to infertility. But if sperm is detected in semen, does it mean that fertility is definitely possible? The answer is no. Does a decrease in the quality of semen affect only the chances of pregnancy? The answer is also no. From the perspective of eugenics, what should we pay attention to? There are many items in the routine semen examination, and there are many functions of sperm, such as energy acquisition, acrosome reaction, fertilization, etc. Poorly functioning sperm can lead to stillbirth, habitual abortion, etc. Studies have shown that sperm motility is closely related to function, and low motility sperm is closely related to poor sperm function. Morphological abnormalities of sperm are directly related to unexplained miscarriage, such as conical sperm malformation, amorphous sperm morphology, etc. Delayed fertilization, follicular division, etc. are also associated with malformed sperm conception. Densitometry of spermatozoa mainly reflects the spermatogenic function of the testes and should be further treated when it is lower than 5 million/ml. The volume, PH value, viscosity, odor, liquefaction time and color of semen can reflect the presence of abnormalities in the accessory gonads and reproductive tract, which are significant for the maturation of sperm and directly affect the quality of semen. Mycoplasma and Chlamydia infections in the reproductive tract can cause destruction of spermatogenic cells, damage sperm cells, cause sperm malformation, and may also affect embryonic development and cause miscarriage. The relationship between poor quality of semen and poor embryonic development has been widely demonstrated. Sperm with low viability or high malformation rate have a high probability of sperm chromatin abnormalities and genetic mutations, which may lead to miscarriage, stillbirth, mental retardation and genetic effects of malformation occurring when the karyotype analysis of peripheral blood cells may be normal, while minor chromatin abnormalities may not lead to morphological abnormalities, but still lead to sperm changes that result in defects. Therefore, from the perspective of eugenics, clear morphological abnormalities, low viability, and reproductive tract infections should be actively diagnosed and treated.