Sperm PH is normal, but no sperm is the occurrence of azoospermia, the causes of which include secondary factors, chromosomal abnormalities, obstructive factors and so on. 1.Secondary factors: (1) Chemotherapeutic drugs: alkylating agents such as nitrogen mustard phenylbutyrate and cyclophosphamide have anti-mitotic and radiation-like effects on spermatogonia. (2) Radiotherapy: radiotherapy can cause temporary azoospermia. (3) Nutrition: Zinc deficiency in humans can prevent sperm production. Severe malnutrition often affects the spermatogenic function of the testes and azoospermia occurs. (4) Heat: sauna, elevated body temperature, long-term high-temperature work, etc. can lead to oligozoospermia, and in severe cases, azoospermia occurs. (5) Endocrine factors: gonadotropin deficiency can cause different stages of spermatogenic blockage. (6) Testicular factors: varicocele, testicular sheath effusion, cryptorchidism, testicular torsion, etc. can cause spermatogenic blockage in patients. (2) Chromosomal abnormality: 11.9%-15% of azoospermia is caused by chromosomal abnormality. 3. Obstructive factors: (1) Congenital factors: such as congenital bilateral absence of vas deferens or congenital absence of seminal vesicles. (2) Acquired factors: ① infection: inflammation of the seminal vesicles and prostate can cause ejaculatory duct obstruction. ② trauma: such as varicocele surgery may damage the vas deferens, such as bilateral damage, azoospermia. ③ Tumor: epididymal and testicular tumors may compress or destroy the vas deferens. ④ Others: local radiotherapy can cause adhesion and fibrosis of epididymis or vas deferens. Patients with azoospermia should go to the hospital in time and receive standardized treatment under the guidance of doctors.