The experimental conditions that adopt to evaluate the friction characteristics of the wet brake axel gear oils at present are commonly high rotary speed,small inertia and low brake pressure,which can not reflect the actual conditions of the wet brake axel,such as low speed,large inertia and high brake pressure.Based on the actual brake conditions of the brake axel,a test method of evaluating the friction characteristics of wet brake gear oils was established.The test method uses the energy flux of friction plate surface to represent the severity of braking condition,which can investigate the influence of brake pressure and different energy flux on the friction characteristics of wet brake gear oils under typical working conditions.The test method was used to study the friction characteristics of common GL-5 gear oil and specific wet brake axel oil on a wet brake bench tester.The results show that the test method has a good ability to distinguish the gear oils with different friction characteristics.