Objective: To observe effect of Letrozole sombined with aspirin on ovulation dysfunction due to polycystic ovarian syndrome(PCOS).Methods: A total of 800 PCOS patients were selected and randomly divided into 4 groups: 200 patients were treated by clomiphene citrate(CC) for 288 courses,200 patients by urinary hCG(HMG) for 224 courses,200 patients by letrozole + TCM(LE1)for 290 courses and 200 patients by letrozole+aspirin(LE2) for 295 courses.After the treatment,incidence of mature follicles,pregnancy rate,m...