Oligospermia is a condition in which an adult man’s semen has a sperm density of less than 20 million sperm per milliliter. Oligospermia is the most common form of male infertility. It is usually uncomfortable and is often associated with infertility. There are many causes of oligozoospermia, which can be roughly categorized into five aspects: 1, idiopathic spermatogenesis: that is, unexplained reduction in spermatogenesis, which is not yet able to clarify its etiology; 2, physical ailments: such as reproductive tract infections are one of the common causes of oligozoospermia in clinical practice, and viral mumps occurring in adolescence in conjunction with orchitis, which can cause damage to the spermatogonial cells of testis. Endocrine disorders, vitamin and trace element deficiencies, varicocele can also inhibit sperm production; 3, drug factors: immunosuppressants such as cyclophosphamide, aminomethylstilbestrol, colchicine and so on can directly or indirectly affect spermatogenesis, in addition to long-term use of large quantities of androgens for some reasons, due to the negative feedback effect of the hypothalamus to reduce the gonadotropin-releasing hormone leading to reduced secretion of gonadotropin, resulting in a reduction or lack of sperm; 4, the use of androgens for a long time. Sperm reduction or lack of; 4, environmental factors: with the progress of social industrialization, harmful substances in the atmospheric environment, some additives in the food, pesticide residues, hormone residues, radiation, high temperature environment, etc. may be spermatogenic epithelium damage to the spermatogonial division of spermatocytes stagnation or cessation, or even irreversible damage; 5, bad habits: some bad habits such as alcoholism, smoking, drug abuse, long time hot bath, sauna can inhibit sperm production. However, many patients are still unable to find a clear clinical cause. Since sperm density fluctuates within a certain range, at least two semen tests are necessary to determine oligospermia, and the semen should be examined without ejaculation for three to seven days before the test in order to correctly reflect the quality of semen. Patients with oligospermia need to be carefully questioned about their medical history, and a detailed physical examination, as well as the necessary laboratory tests, is an important means of finding the cause of the disease. It is important to exclude or clarify whether the patient has disorders that affect sperm production such as varicocele, chronic inflammation of genitourinary system, cryptorchidism, endocrine disorders, vitamin and trace element deficiencies, pathogenic microbial infections, and drug influences, so as to provide a basis and direction for clinical treatment.