Abstract: The concentration of serum antibody of the softshelled turtle was measured using SRID.The concentrations of non-immune serum and immune serum antibodies wer e about 9.623 mg/mL and 17.097 mg/mL respectively.The later was about two folds as much as the former.This showed that the level of serum antibody of turtle would increase quickly and keep higher level when it is stimulated with antigen.