Finasteride is a basic drug for the treatment of prostatic hyperplasia and prostatitis in China. It is a synthetic 4-nitrosteric hormone compound and a resistant hormone drug. It can selectively inhibit 5α - reductase, inhibit the process of transforming testosterone into 5α - dihydrotestosterone (DHT), and reduce the level of androgen Chemicalbook in prostate cells. Serum prostate-specific antigen decreased, enlarged prostate volume decreased, urine flow rate increased, thereby reducing the symptoms of patients, to achieve the purpose of treating prostate hyperplasia. The action of the drug is characterized by the selective blocking of androgen stimulation of the prostate gland, but it rarely affects the sexual function of men.