Azoospermia can be divided into two categories, the first is testicular spermatogenic dysfunction spermatozoa can not be produced, also known as bona fide azoospermia, the second is testicular spermatogenesis is normal, but the vas deferens obstruction spermatozoa can not be discharged out of the body, also known as obstructive azoospermia. (1) Genetic diseases, autosomal or sex chromosome abnormalities affecting testicular spermatogenesis, such as Klinefelter’s syndrome, etc.; (2) congenital testicular anomalies, testicular developmental abnormalities, or testicular positional abnormalities that can lead to spermatogenesis disorders; (3) testicular lesions such as testicular trauma, inflammation, torsion, and testicular vascular disease; (4) endocrine disorders with hyper or hypo functioning pituitary gland; and (5) endocrine disorders such as hyper or hypo functioning pituitary gland, which is also known as azoospermia. (4) Endocrine diseases, such as pituitary hyperfunction or hypopituitarism, pituitary tumors, adrenal hyperfunction or hypopituitarism, hyperthyroidism or hypothyroidism, can affect spermatogenesis and result in azoospermia; (5) Severe systemic diseases and malnutrition can lead to azoospermia; (6) Radiation damage and medications, especially cytotoxic medications, etc., can lead to azoospermia in case of severe damage to spermatogonial cells of testes. The patient’s secondary sexual characteristics, libido and sexual function are normal, and the testes have normal development, but no sperm is discharged due to the obstruction of the vas deferens. The causes of azoospermia include: (1) congenital malformations, such as ectopic head of the epididymis, epididymal duct atresia, and absent or undeveloped vas deferens; (2) infection with gonococcus and tuberculosis and other bacterial infections that can lead to the obstruction of the epididymis and the vas deferens; (3) epididymal cysts that compress the epididymal ducts and lead to the obstruction of the epididymis; and (4) injuries that can lead to the obstruction of the vas deferens. After centrifugation and microscopic examination of the sediment, no spermatozoa were found in three times, and the diagnosis of azoospermia can be confirmed, and the etiology needs to be further clarified. Physical examination, pay attention to the development of secondary sexual characteristics and external genital development, if the testicular volume is less than 10 milliliters, the texture is abnormally soft, often suggesting poor testicular function, palpation should pay attention to the epididymis, vas deferens with or without deformities, nodules. Endocrine examination, serum FSH (follicle stimulating hormone), LH (luteinizing hormone), PRL (prolactin), T (testosterone), DHT (dihydrotestosterone) can help to identify primary testicular failure or secondary testicular failure. Testicular ultrasound can detect gross testicular lesions, and testicular biopsy can provide a more definitive diagnostic and therapeutic basis.