Abstract: A self-locking electromechanical actuation system to gimbal a high thrust liquid rocket engine is put forward to meet the demands of the batch production and the triplex horizontal preparation for an agile launching of China’s new generation launch vehicles. A self-locking module is designed, a tandem compact electro-mechanical actuator and a control algorithm to suppress structural resonance are adopted. Ground experiments are carried out. It is shown that, the requirements of a long term horizontal transportation, a horizontal testing to tolerate the engine gravity effect, the control of the low frequency resonance of a liquid engine, and easiness for batch production, shall all be satisfied, laying a good foundation to facilitate the development of the next generation medium-sized launch vehicle in China.