The utility model relates to a fuel-cell car engine power testing device, and belongs to the technical field of car engine performance test. The testing device comprises an inverter connected with the electrical energy output end of a fuel-cell engine, a motor matched with the inverter, and a dynamometer, wherein, the motor is connected with the dynamometer by a shaft coupling. The device uses the dynamometer of a conventional car engine as load, and does not use electronic load. The testing principle is that the electrical energy of the fuel-cell engine is converted into mechanical energy by the motor through the DC/DC or DC/AC inverter, and then, the torque and the power dynamic performance index of the fuel-cell engine are tested by the dynamometer. The utility model has the advantages that the utility model does not use the electronic load, but uses the dynamometer as the load. Thus, the testing result can visually reflect the dynamic performance of the car engine, and the dynamic performance is approach to the actual dynamic performance on a car.