Male infertility is the result of multiple diseases and/or factors and is usually divided into pre-testicular, testicular and post-testicular segments depending on the disease and factors interfering or affecting the reproductive link. Pre-testicular factors: endocrine causes of male infertility, the impairment of reproductive function in this group of patients is secondary to hormonal imbalance in the body. 1. Thalamic disorders (1) gonadotropin deficiency (2) selective luteinizing hormone (LH) deficiency (3) selective follicle stimulating hormone (FSH) deficiency (4) congenital hypogonadotropic syndrome 2. Pituitary disorders (1) pituitary insufficiency (2) hyperprolactinemia 3. Endogenous or exogenous hormonal abnormalities (1) excess estrogen and/or androgens (2) excess glucocorticoids (3) hyper- or hypothyroidism, thyroid function abnormalities account for about 0.5% of the causes of male infertility. Testicular factors (a) congenital abnormalities 1. chromosomal or genetic abnormalities 2. cryptorchidism 3. androgen dysfunction, mainly androgen insensitivity syndrome, and peripheral androgen resistance, the former mainly due to abnormalities in a link of the androgen signaling process, the latter includes mainly: 5α-reductases deficiency (5α-reductases deficiency) and androgen The latter includes 5α-reductases deficiency and abnormal androgen receptor. 4, other rare syndromes: myotonic dystrophy, orchidrosis, support cell only syndrome, etc. (ii) gonad-toxin Commonly, there are radiation, drugs, food, living and working environment factors, etc. (iii) Systemic diseases Systemic diseases that often cause infertility include renal failure uremia, cirrhosis and hepatic insufficiency, sickle cell disease, etc. (iv) infection (orchitis) after puberty mumps 30% combined with orchitis, often unilateral, bilateral incidence of 10% to 30%, testicular atrophy is the most common serious consequences of viral orchitis, but it is less common in bacterial infections. (E) Testicular trauma and surgery The testicles are easily injured, which can lead to testicular atrophy in addition to stimulating an abnormal immune response, both of which can lead to infertility; medical injury to the testicular vessels and vas deferens can also lead to infertility. In addition, testicular vascularity, testicular torsion, and immunological factors can cause infertility. Third, post-testicular factors (a) vas deferens obstruction vas deferens obstruction is one of the important causes of male infertility, obstructive azoospermia in about 7% to 10% of male infertility patients. (1) Cystic fibrosis (CF): an autosomal recessive disorder, almost all male patients with cystic fibrosis have congenital bilateral absence of the vas deferens (CBAVD). (2) Yong syndrome: the main manifestations of the triad: chronic sinusitis, bronchiectasis and obstructive azoospermia. Spermatogenic function is normal, but azoospermia is manifested due to obstruction of the epididymis by concentrated material. The success rate of surgical reconstruction is low. (3) Idiopathic epididymis obstruction: This disease is rare, and 1/3 of patients have cystic fibrosis gene mutation, which may be related to cystic fibrosis. (4) Adult polycystic kidney disease (APKD): an autosomal dominant disorder with multiple cysts in the internal organs of the patient, which can lead to infertility when there are obstructive cysts in the epididymis or seminal glands. (5) Ejaculatory duct blockage: accounts for 5% of the causes of azoospermia, and can be congenital such as Mullerian duct cyst, Wolffian duct cyst or atresia, or acquired such as seminal vesicle stones or scars from surgical inflammation. 2. Acquired obstruction. It is mainly due to reproductive system infection, vasectomy, surgery in the groin area, and accidental injury to the vas deferens. In addition, inflammatory reaction around the vas deferens after the application of patch in hernia repair leads to vas deferens obstruction. 3.Functional obstruction. Any factor that interferes with nerve conduction in the vas deferens and bladder neck can lead to non-ejaculation or retrograde ejaculation, with common causes such as nerve injury and after taking certain medications. (B) Sperm function or motility disorders 1. cilia immobilization syndrome (Immotile cilia syndrome). This disease is due to the reduction or loss of motility of sperm due to abnormal sperm motility or axons, resulting in fertility disorders. 2. Maturation arrest. It is commonly seen after vasectomy recanalization. Due to the long-term high pressure in the epididymal duct after ligation, the spermatozoa do not acquire normal maturation and motility when passing through the epididymis after recanalization, so the vitality is low, but the number of spermatozoa can be normal. (iii) Immunological infertility 2% to 10% of infertility is related to immunological factors. Common causes include testicular trauma, torsion, biopsy, infection or blockage of the vas deferens, post-anastomosis surgery, etc. (iv) Infection It has been reported that 8% to 35% of infertility is related to infectious inflammation of the male reproductive tract, mainly infection leading to obstruction of the vas deferens, anti-sperm antibody formation, bacteriospermia, the role of leukocytes in semen, and abnormal seminal plasma. (E) sexual intercourse or ejaculatory dysfunction hypoactive sexual desire, ED, ejaculatory dysfunction is a common cause of infertility, diabetes, inflammation of the bladder urethra, abnormal bladder neck muscles, hypospadias, surgery or trauma injury to the nerves can also lead to non-ejaculation or retrograde ejaculation; bad sexual habits such as too frequent intercourse, application of stimulants, lubricants, etc. can also affect fertility. Fourth, idiopathic etiology idiopathic infertility refers to male infertility can not find a clear cause of the link that affects reproduction may involve one or more links before the testes, the testes themselves, after the testes. The current tendency is to be associated with genetic or environmental factors, etc.