Erectile dysfunction (ED) is a common male disease and frequently encountered in Andrology. PDE5 inhibiter can competitively inhibit the hydrolysis of cyclic guanosine monophosphate (cGMP), increase the cGMP concentration in the smooth muscle cells of the corpus cavernosum penis, and achieve the therapeutic effect on ED. Tadalafil can elevate the level of cGMP in the corpus cavernosum and effectively improve ED of various causes and degrees. Tadalafil therapy for ED, characterized by long efficacy, high safety, easy acceptance by patients and their partners, and obvious promotion of patients'self-confidence and natural experience in sexual activities, can achieve satisfactory physiological and psychological results and effectively improve the quality of patients' sexual life. Therefore tadalafil deserves an extensive clinical application in the treatment of ED.