The transmitting force distribution of a V-ribbed belt on a pulley was studied experimentally and theoretically. The experimental results revealed that the transmitting force existed while the load transmitting power was not applied. The transmitting force changes linearly from the entrance to the exit of the pulley under a relatively high axial force condition. The transmitting force distribution curve shifts to the right (on the driven pulley) or to the left(on the driving pulley) with increase of load. Under a relatively low axial load condition, partial slippage between the pulleys and the belt occurs. An extended Firbank’s equation which has been formulated originally for flat belts, is applicable to analyzing the force distribution. The combination of Firbank’s equation with Euler’s equation gives a good explanation for the transmitting load distribution on the driving pulley in particular.