The concentration and number of sperm are closely related to male fertility and are very important. According to the WHO Laboratory Manual for the Examination and Processing of Human Semen (5th edition) issued by the World Health Organization in 2010, a total sperm count of less than 39×106 or a sperm concentration of less than 15×106/ml is called oligospermia. If the sperm concentration is less than 5×106/ml, it is considered severe oligospermia. There are many causes of oligospermia, such as cryptorchidism, endocrine diseases, abnormal Y chromosome structure, severe varicocele, and even long-term overheated baths can reduce the spermatogenic function of the testes and decrease sperm production. A single sperm concentration is not an absolute influence indicator of male fertility. Some men have a sperm concentration of about 15×106/ml, which can also conceive the female partner, and has a certain relationship with the ability of the spouse to conceive. It is common that patients with oligospermia often have a combination of low sperm motility and increased malformed sperm, resulting in low fertility due to the low number of sperm with fertilizing ability in the semen. The result of only 1 semen test is lower than the reference value and cannot be considered as oligospermia. It is recommended that abstinence is generally 2-7 days for 2 consecutive re-examinations. Oligospermia can only be determined after several semen test results are below the reference value within the standard abstinence time. The older you get, the weaker the sperm production function of the testes and the lower the sperm concentration. The cause of oligospermia is complex, especially in severe oligospermia where the efficacy of drugs, hormones or surgery is not satisfactory, but in vitro fertilization or intracytoplasmic injection of single spermatozoa has better results.