According to the changing law of the rotational speed after original flywheels rotational inertia system produced a brake, in this work, computer was used to gather real-time parameters of spindle speed, brake pressure, brake torque, brake distance ect. With the help of direct current motor and four-quadrant speed regulation system combined with the control algorithm of electrical simulation system for mechanical rotational inertia, simulating the larger moment of inertia by making use of small mechanical flywheel system was realized. As a result, the reduction of traditional mechanical flywheel was accomplished and the stepless adjustment of inertia was realized by the application of mechanical inertia and electric inertia hybrid simulation method.