Abstract: It was demonstrated that soft..shelled turt le, Trionyx sinensis, with bacterin T3 had anamnest ic response that was situated between the f ish and mammal. It possessed these characters: ( 1) the anamnestic and primary response differed significantly in peak stage of IAT of soft..shelled turtle, and its ratio reached two or so; ( 2) antibody of primary response produced quickly , which got to the highest level on about the 16th day after the second immunization, but its disappearing speed was slower than producing one; ( 3) the producing rate of IAT of anamnestic response went up faster than that of the primary, but the dropping rate was slower.