Gallic tannins have extensive bioactivities functions，including antioxidant，antitumor and anticancer. In order to investigate the extraction technology of Chinese gallnut tannin by ultrasonic, the effect factors，including the volume fraction of HCl , the volume fraction of ethanol, ultrasonic temperature and the ratio of material were optimized through orthogonal tests L₉（3⁴）on the basis of single factor experiment . The result showed the optimal extracting conditions were as follows: hydrochloric acid volume fraction 1.0%, ethanol volume fraction 50%, ultrasonic temperature 40 ℃, the ratio of material to liquid was 1∶30(m∶V). Under the optimal conditions，the extraction rate of Chinese gallnut tannin was 10.97%.