The invention provides a full load test device and a test method. The full load test device comprises a power source, a compensation capacitor, a detecting device, a shunt reactor, a voltage regulatorand an intermediate transformer, wherein the shunt reactor is serially connected with a tested device, is then parallelly connected with the compensation capacitor and is then connected with the power source through the intermediate transformer and the voltage regulator for regulating the voltage of the intermediate transformer; and the exit of the tested device is connected with the detecting device. The test device provided in the invention overcomes the problems that the existing test device can not reach the rated design capacity in field operation and whether a produced compensation device is qualified can not be detected.