Abstract: Objective：To evaluate the value of transvaginal ultrasonographic (TVS) measurement of polypoid mass in uterine cavity in identifying postmenopausal endometrial cancer. Methods：Totally 520 postmenopausal women accepted hysteroscopy(Hy) for polypoid mass in uterine cavity by TVS. Characteristics of postmenopausal women with endometrial cancer were analyzed. The sensitivity and specificity of TVS and Hy diagnosing endometrial cancer were calculated with the histological results being the gold standard. The best cutoff point of the size of polypoid mass by TVS diagnosing endometrial cancer was determined by ROC curve. The positive predictive value (PPV) and the negative predictive value (NPV) of the best cutoff point were calculated. Results：The postmenopausal endometrial cancer was correlated with postmenopausal bleeding (PMB), larger polypoid mass, and more uterine hydrops, but not with age, age at menopausal, years of menopausal or thickness of endometrium. The prevalence of postmenopausal endometrial cancer with PMB was 6.4 times higher than thoses without PMB. The accuracy of Hy diagnosing postmenopausal endometrial cancer was higher than that of TVS. The best cutoff point of the size of polypoid mass by TVS diagnosing endometrial cancer in asymptom postmenopausal women was 14.5 mm, with the PPV 10.75% and the NPV 99.14%. The best cutoff point of the size of polypoid mass by TVS diagnosing endometrial cancer in PMB postmenopausal women was 18.5 mm, with the PPV 55.56% and the NPV 91.94%. Conclusions：For asymptom PMB postmenopausal women, the size of polypoid mass in uterine cavity by TVS over 14.5 mm as indication of Hy is reasonable. The prevalence of endometrial cancer is high in PMB postmenopausal women with polypoid mass found by TVS, thus Hy should be provided.