Azoospermia is defined as a condition in which no sperm are found on multiple semen tests (usually more than 3, and on semen tests, if no sperm are seen on microscopic examination, centrifugation is required to look for sperm). This disease is one of the main causes of male infertility. If necessary, combined with history, physical examination, seminal plasma biochemistry, testicular biopsy, endocrine hormone measurement, karyotyping and Y chromosome microdeletion can be done to help identify obstructive azoospermia or non-obstructive azoospermia. Azoospermia is categorized into the following two types: 1. Non-obstructive azoospermia (NOA): a disorder of spermatogenesis in the testes, which fails to produce sperm or produces only a very small amount of sperm, resulting in the absence of sperm in the semen. Specifically can be divided into: ① hereditary diseases: autosomal or sex chromosome abnormalities, affecting testicular spermatogenesis, such as Klinefelter’s syndrome, etc.; ② congenital testicular anomalies: abnormal testicular development or abnormal testicular position can make spermatogenesis impaired; ③ testicular lesions: such as testicular trauma, inflammation, torsion and testicular vascular disease; ④ endocrine disorders, hypopituitary hyper or hypopituitary, pituitary tumors, adrenal glands, and other endocrine disorders. Endocrine diseases, pituitary hyperfunction or hypopituitarism, pituitary tumor, adrenal hyperfunction or hypopituitarism, hyperthyroidism or hypopituitarism can affect spermatogenesis and result in azoospermia; ⑤ Severe systemic diseases and malnutrition can lead to azoospermia; ⑥ Radiation damage and medicines, especially cytotoxic medicines can damage the testicular spermatogenesis cells, which can lead to azoospermia in severe cases. 2. Obstructive azoospermia (OA): the absence of sperms in semen caused by obstruction of the vas deferens. The patient’s secondary sexual characteristics, libido, sexual function is normal, testicular development is normal, spermatozoa are produced, but no sperm are discharged due to the obstruction of the vas deferens. The causes include: ① congenital malformations, common ectopic epididymal head, epididymal duct atresia, vas deferens is missing or not developed; ② infection with gonococcus, tuberculosis and some other bacterial infections, which can cause obstruction of epididymis and vas deferens; ③ epididymal cysts compress epididymal ducts and cause obstruction; ④ injury to make the vas deferens blocked. For patients with non-obstructive azoospermia, adoption, harboring, or sperm donor assisted reproductive technology can be considered according to the female’s condition. For obstructive azoospermia, it is first necessary to search for the cause of the disease and give priority to recanalization (e.g., vasovaso-vas deferens anastomosis, vasovaso-epidididympanic anastomosis, transurethral ejaculatory duct cystotomy, etc.), in order to achieve the possibility of normal reproduction. If recanalization fails or does not meet the indications for surgery, percutaneous epididymal sperm aspiration (PESA) or percutaneous testicular sperm aspiration (TESA) can be used to obtain sperm for intracytoplasmic sperm injection (ICSI) to achieve fertility.