Variable thrust LREs (Liquid-Propellant Rocket Engines) which can be used for thrust modulation is an ideal choice for space propulsion. Flux controlling technology which is the core technology of variable thrust LREs is also the emphases and difficulties on the research of variable thrust LREs. Based on the conclusions of variable thrust LREs's technology, the pivotal technology related to proportional solenoid actuator, valve port and dynamic characteristics are analyzed. It proves the feasibility of the technology through the comprehensive research, and will provide an important technical support for future application.