The minimal inhibitory concentration (MIC) and the minimal bactericidal concentration (MBC) of 86 kinds of Chinese herbal medicines (CHMs) on Aeromonas hydrophila were examined in vitro by the microdilution method. Then the optimum mixtures of CHMs which can inhibit the A. hydrophila were found through orthogonal test design. The result showed that Galla chinensis, Fructus schisandrae and Fructus mume had the strongest inhibitory effect on A. hydrophila,with the MIC and MBC as 12.5 mg/ml. In conclusion, G. chinensis, F. schisandrae and F. mume were the better drugs that can cure the disease caused by the A. hydrophila in aquatic animals. The results of orthogonal tests showed that the mixture of Acacia catechu, G. chinensis, F. schisandrae and F. mume with the proportion of 4∶2∶4∶1 and 1∶2∶2∶4 had the best MIC and MBC on A. hydrophila.