In this paper, the authors have designed a set of high torque rigidity stabilizing loops for heavy load Inertial Stabilized Platform, described the control method and introduced the detailed hardware design. Static test and dynamic test are accomplished including the swing table and flight. As a result, the steady-state error of stabilizing loop is ±10.5" in the max disturbed torque, and damping capacity of platform angular rate is better than . The stabilizing loop works well and is reliable. It meets the requirement of the gravity gradient dynamic measurement.