An inertia braking test system and a control method is provided, wherein the inertia braking test system is composed of an inertia brake test system, a sensor system and a tested object. An actuating device is connected with the inertia brake control device through a ball stud. The actuation function of the inertia brake control device with two degrees of freedom along the front-and-rear direction and the up-and-down direction of the vehicle is realized. The movable chassis realizes the mobile function of the system. The acceleration sensor can sense the acceleration of the movable chassis. Each force is tested by the first force sensor, the second force sensor and the third force sensor. The displacement data is measured by the first displacement sensor and the second displacement sensor, so that a movable brake system test is achieved.