Abstract: Studies on the optimum process of extracting flavonoids from bamboo leaves were carried out by the method of orthogonal test, and flavonoids was determinated using rutin as reference substance. Bamboo leaves extracts were isolated and purificated by vacuum thin film concentration,ultrasonic decolorization, and adsorption with macroreticular resin Diaion HP-20. The result shows that the optimum process of extraction was 80%(volume fraction) ethanol, 10 times of the weight of raw material, extracting one time for 5min. The extracts were eluted on Diaion HP-20 resin column with a successive gradient elution system of H2O-MeOH at 5mL/min flow rate to obtain extract of flavonoids after vacuum concentration. The purity of flavonoids was 76%.