This research designed and produced a power test machine for locomotives braked by pneumatic brake calipers, also known as a power meter. Unlike the inertial roller power test machine that can not simulate the load of the locomotive driving road, this research is to calculate the torque and brake horsepower of the car through the brake roller force generated by the pneumatic caliper brake, which is a function of the approximate eddy current braking system.The braking efficiency of the pneumatic braking system in this study has 17% at the input air pressure of 0.4Mpa. The braking torque efficiency can reach 25% under the load when the input air pressure is 0.1Mpa.