Abstract: Inertial sensor technology and wireless bluetooth capture technology are adopted to develop the portable test system of isotonic muscle contraction joint power curve. The paper elaborates the internal structure and data processing method of the test system. The test system uses a cubic spline interpolation to interpolate, which make it possible to easily test the peak power curve of isotonic muscle contraction joints under different loads and to be taken into classrooms and training places. It can be widely applied to athletes’ selection and training.