Circulation precooling driven by pump is used by Large-Thrust Hydrogen/Oxygen rocket engine of CZ-5 Launch Vehicle. The Circulation precooling pump of liquid hydrogen is driven by a permanent magnet synchronous motor. The circulation precooling control system control the motor of circulation precooling pump by sensorless vector control technology. This paper introduces the scheme of circulation precooling control system, expounds the key technology design, such as coordinate transformation and mathematical modeling, space vector pulse width modulation technology, sensorless control technology and so on, The two cable design methods are compared and analyzed in this paper. The research contents of period of oscillation, pump resonance in liquid nitrogen and motor stall in liquid hydrogen are simulated to verify the system design in liquid nitrogen and liquid hydrogen environment. The results show that the circulation precooling control system with sensorless vector control technology has the advantages of simple installation, flexible speed regulation and strong adaptability to load change.