The first step is to take a medical history to find out if there are any diseases affecting fertility, such as post-pubertal mumps combined with orchitis, gonorrhea, trauma to the scrotum, and surgery to the external genitalia and groin area. A thorough physical examination is then performed, including developmental, nutritional and mental status, but with emphasis on the secondary sexual characteristics and reproductive organs, such as the laryngeal nodes, beard, pubic hair distribution and the presence of breast feminization, as well as the penis, urethra, prostate, testicles, epididymis and spermatic cord. The auxiliary tests to be performed are: ① Semen analysis, sperm morphology analysis, seminal plasma biochemistry: it helps to understand male fertility and is a mandatory test for infertility. ②Prostate fluid examination: one of the necessary tests in case of semen non-liquidity. ③CT, UU-DNA examination to understand the presence of non-gonococcal urethritis. ④Endocrine examination (sex hormone six): to understand testicular function and spermatogenic function of testicles. ⑤ Ultrasound examination of scrotum to confirm the presence of varicocele. ⑥Immunological examination (anti-sperm antibodies): to exclude infertility caused by immunity. ⑦ Testicular biopsy: for patients with azoospermia or oligospermia. ⑧Karyotype analysis: used for malformations of external reproductive organs, testicular dysplasia and azoospermia of unknown origin. ⑨ Sperm DNA fragmentation: commonly used as one of the tests for habitual abortion.