Considering the shortcomings of single rate-loop servo control composed of rate gyro for stabilization of inertia platform, a dual rate-loop cascade control structure is presented, which uses the DC tachometer to constitute the digital inner loop, and uses the rate gyro to constitute the digital outer loop. In the tracking control system, using PI controller, we achieved a ternary closed loops cascade control mode which is constituted of current, inner velocity and outer velocity loop, and then, compared it with a dual closed loops cascade control mode which is constituted of current, and velocity loop. The experimental results show that the single rate-loop cascade control mode is better in high- frequency disturbance, while dual rate-loop cascade control mode gets better stabilization precision in low-frequency disturbance and better functions of rejecting friction disturbance.