Azoospermia is defined as the absence of spermatozoa in the ejaculated semen after routine analysis and centrifugal microscopy. Clinically, it usually requires three or more consecutive semen examinations to confirm the diagnosis, and each semen examination should be performed at least one week apart, and conditions such as non-ejaculation and retrograde ejaculation should also be excluded. In clinical practice, male factors account for about 50% of the causes of infertility, and among infertile men, azoospermia accounts for about 5% to 20%. The normal volume of the unilateral testis in domestic men is between 12-25 ml, which contains testicular supply vessels, spermatogenic tubules, testicular interstitium and other structures. The surface of the testis is covered with plasma membrane and the deep part is a white membrane composed of dense connective tissue, which thickens at the posterior edge of the testis to form the longitudinal septum. The connective tissue of the mediastinum extends radially into the testicular parenchyma, dividing the testicular parenchyma into about 250 conical lobules, each of which contains one to four curved and elongated spermatogenic tubules. The straight seminiferous tubules enter the longitudinal septum of the testis and anastomose with each other to form the testicular net. The loose connective tissue between the seminiferous tubules is called the testicular interstitium. The testicular network merges into 15-20 testicular output tubules that connect to the epididymis. Spermatozoa are produced in the germinal tubules and enter the epididymis through the structures of the rectus seminiferous tubules, the testicular reticulum, and the efferent tubules. Sperm develop and acquire the ability to fertilize after about 15-20 days in the epididymis. They enter the vas deferens through structures such as the head of the epididymis, the body of the epididymis, and the tail of the epididymis, and are discharged through structures such as the vas deferens, the ejaculatory duct, and the male urethra. Accordingly, patients with azoospermia can be divided into obstructive azoospermia and non-obstructive azoospermia according to the presence or absence of obstruction in the vas deferens.