Abstract: Uterine artery pulsatility index（PI） and resistance index（RI） by the transvaginal color Doppler ultrasound can reflect the changes of endometrial blood flow，which showed the status of endometrial development and endometrial function. In patients with polycystic ovary syndrome（PCOS）， the factors influencing the endometrial blood flow include hyperinsulinemia，hyperandrogenism，the increased luteinizing hormone， obesity，hyperlipidemia and hyperactivity of renin-angiotensin system. These factors induce the impaired endometrial function and lowed endometrial receptivity. Endometrial function can be improved by medical treatment.

Key words: Polycystic ovary syndrome, Endometrium, Ultrasonography, doppler, color, Hemodynamics, Blood flow velocity