In order to reveal the shifting mechanisms for CVT using a metal V-belt, mean coefficients of friction and shifting gradient; dR/ds were introduced. Belt motion in the pulley groove was characterized using the mean coefficients of friction as parameters which identify the slippage condition of the belt in the pulley groove. The experimental results showed that thrust force and sliding speed influenced the mean coefficients of friction. It was also revealed that the shifting gradient was not influenced by transmitting torque.