Objective To investigate a method determining the number of preconditioning cycles in uniaxial tensile test on soft tissues by calculating the decay rate of strain energy. Methods The abdominal skin of healthy New Zealand rabbits was selected as study object, from which strip specimens were obtained in directions parallel to linea alba (0°)and perpendicular to linea alba(90°). Then the uniaxial preconditioning tests with 15% preconditioning strain were performed on these specimens. Load displacement preconditioning data were obtained, and transformed into the stress strain data correspondingly. The preconditioning cycles (n values), at the decay rate of strain energy being 5% and 10%, respectively, were then calculated by MATLAB programme when n values satisfy the inequality η=Wn－Wn－1Wn－1×100%≤5% or≤10%（Wn signifies the strain energy loss in the nth preconditioning cycle）. Results When the decay rate of strain energy was 5%, the number of preconditioning cycles in 0° and 90° direction was 11.11 and 13.67, respectively. When the decay rate of strain energy was 10%, the number of preconditioning cycles in 0° and 90° direction was 6.67 and 7.78, respectively. Conclusions By calculating the decay rate of strain energy, the number of preconditioning cycles in uniaxial tensile on soft tissues can be quantified, which could help provide the research basis for standardization of biomechanical testing on soft tissues.