Sperm head defects refer to the presence of abnormalities in the head of sperm, including large head, small head, indeterminate head and round head. Since the sperm head contains the nucleus and acrosome, the lack of nucleus can directly affect the lack of genetic material, which can cause embryonic sterility, embryonic development arrest or miscarriage. The acrosome contains many enzymes, the deficiency of which can directly affect the ability of sperm to cross the radial crown, zona pellucida, and oocyte membrane, and the occurrence of sperm-egg binding disorders causing infertility. There are many causes of sperm head defects, among which diseases such as varicocele and cryptorchidism are more common. The former is mainly due to the fact that it can lead to stagnation of blood flow in the scrotum, causing toxic substances such as cadmium to enter the testes, which affects the spermatogenic function of the testes and leads to an increase in the proportion of defective sperm. The latter is mainly because the local temperature of the testes is too high, leading to testicular dysplasia, causing an increase in the proportion of sperm with head defects. Sperm head defects should be treated promptly by a doctor to avoid delaying treatment.