This paper proposes an in-situ electric energy acquisition technology for power generation by drawing propellant from a rocket engine. The high-pressure fuel is drained from the engine with abundant power， and then returns to the engine after power generation by the energy conversion device. This technology can greatly reduce the weight of the power supply system. A 1 200 kN liquid oxygen kerosene engine is taken as an example， and a lightweight principle prototype of 35 MPa constant speed generator and rectifier transformation is developed. A test system for driving a two DOF electro-hydrostatic actuator system is built. The test results show that the system can meet the instantaneous power demand of the servo system with the rated high voltage of 270 V and the peak power of a high current of 40 kW， and also meet the power demand of the 28 V general rocket borne electronic equipment. This technology is expected to provide a power supply scheme with lightweight， high safety and high-power for multi electrification / full electrification of launch vehicle equipment in the future.