China's first prototype of a new ion rocket engine with mercury as propellant passed the ministerial appraisal in Lanzhou Institute of Physics, Ministry of Space. Ion rocket engine is a kind of electric rocket and a new advanced technology in the world. Its purpose is to accurately maintain the position and control the attitude after the satellite is sent into space orbit by a rocket with high thrust. The rocket engine with mercury as propellant is technically difficult and is still in the experimental stage internationally. Its volume is very small. The control precision is high. It has been used for a long time and adapted to the development trend of modern long-life satellites. Some famous rocket engine experts in China believe that this LF8 ion rocket engine has reached the international advanced level of its kind.