The brake performance of automobiles is one of the important factors in safety driving. As an emphases item in vehicle detection, the brake force affects the brake deceleration, brake distance, brake time and other performance directly. The roller opposite forces type automobile brake test method and flat tester detection method were analyzed briefly. And a new on-line test system was designed by measuring the wheel torque to test the brake force. The principle of the new test method was elaborated. It lays foundation for brake force testing.