Normal male sperm density should be above 4000 per milliliter, if the density is below 2000, it is oligospermia. Oligospermia is a common clinical phenomenon. The cause of oligospermia is still unclear, and the sperm density test is prone to error. The diagnosis of oligospermia requires a series of laboratory tests, including reproductive hormone tests, prostate urogenital tract infection tests, spermatic cord vascular examination, and so on.