Abstract: To investigate the wearing of friction discs, the working principle of wet shifting clutches is studied. The oil pressure and rotation speed characteristics of wet shift clutches are studied. Mathematical model for calculating the wear of friction disc is set up by numerical fitting, and the wear condition coefficient confirmed based on spectral analysis of experimental result, the relationship between friction disc wear and elements such as oil pressure and rotating speed described. After 18000 times of clutch shifting experiments, the functional relation between wear and shifting time is attained. It was proved that the wear of wet shifting clutch can be expressed through oil pressure, rotation speed and times of shifting.