Abstract: The method for determining rutin content of Populus×canadensis Moench. leaves was developed by high performance capillary electrophoresis（HPCE）. Sample was extracted with methanol by ultrasonic.The optimum determination conditions were investigated experimentally and the results were as follows: the running buffer of 50 mmol/L borate (pH=9.3), injection time with pressure of 5 s,temperature of 25℃,applied voltage of 20 kV,detection wavelength of 254 nm. Under the optimum conditions, a good linearity between peak area and concentration of rutin was found.The average recovery is 98.58% and the method is accurate. Meanwhile, the developed method was utilized to investigate the variation of rutin content during the growth of P.×canadensis leaves.