An optical feedback cavity ring-down (OF-CRD) technique,based on the OF effect of diode laser,was developed for accurate high-reflectivity measurement of cavity mirrors.The amplitude of the OF-CRD signal was enhanced to be about two orders of magnitude larger than that without OF effect.The high-reflectivity of the cavity mirror,measured by the OF-CRD at four RDC lengths,is in excellent agreement and statistically determined to be 99.935 6±0.000 8%.The OF-CRD and pulsed-CRD techniques,both based on the exponential decay measurement,were experimentally compared.The measurement accuracy of the OF-CRD is much higher than that of the pulsed-CRD,due to higher beam-propagation losses caused by mode-mismatching and mode beating effects in the pulsed-CRD experiment.