There are about three clinical conditions that cause male azoospermia: 1) congenital testicular hypoplasia, which causes impaired semen production; 2) vas deferens obstruction caused by various reasons; and 3) retrograde ejaculation. Congenital testicular insufficiency: normal semen is continuously matured by spermatogonia in the testes, if the testes are atrophied or insufficiently developed it will affect the maturation or generation of spermatogonia, resulting in congenital azoospermia, this condition can generally be clearly diagnosed through scrotal ultrasound examination and testicular aspiration biopsy, there is no good treatment for congenital azoospermia. Vas deferens obstruction: In adults, the length of vas deferens is 40 cm, one on each side, and the two ends of vas deferens are linked to epididymis and seminal vesicles. Bilateral vas deferens obstruction causes failure of semen ejection, and the common causes are vas deferens tuberculosis, epididymitis, reproductive tract tumor and surgical injury. To make a definite diagnosis, vasovasography can be performed by directly puncturing the vas deferens or by surgically cutting open the skin to find the vas deferens and injecting the contrast agent. Generally, it can be cured by performing recanalization surgery. Retrograde ejaculation: It is a condition in which the feeling of ejaculation is obvious when you reach the climax of sexual life, but you cannot see the semen ejected out of the body, but it enters the bladder, and generally the sperm will be found in the urine after ejaculation and urine examination. This condition is caused by a dysfunctional urethral sphincter causing the bladder neck to not close. A definitive diagnosis requires urine collection after ejaculation and examination of urine routine. Treatment can be cured by bladder neck surgery.