The invention relates to a series-parallel connection composite electromechanical stable platform device, and relates to a device for stably adjusting equipment with the requirement on stability. The series-parallel connection composite electromechanical stable platform device comprises an outer frame and an inner frame arranged in the outer frame, the outer frame comprises a base, an azimuth axis part and a pitch axis part, the azimuth axis part is movably connected onto the base, the pitch axis part is movably connected onto the azimuth axis part, and the inner frame is rigidly connected with the pitch axis part. The inner frame comprises a supporting rack, a stable platform, an actuator, a ball hinge and a rigid connecting rod, one end of the supporting rack is rigidly connected with the pitch axis part, the other end of the supporting rack is connected with the stable platform via the ball hinge, and the actuator is disposed on the supporting rack and drives the stable platform via the rigid connecting rod. The series-parallel connection composite electromechanical stable platform device is simple in structure, the weight of the stable platform is lightened, requirements to an actuating motor are greatly reduced, mechanical response speed is increased, and mechanical natural frequency of a mechanical body is greatly increased.