The High-thrust LOX/LH2 staged combustion cycle engines adopts variable thrust adjustment which can achieve the best thrust control and optimize the best carrying capacity. Based on the electromechanical servo-controlled engine thrust adjustment scheme, the closed-loop control flow regulation technology of the regulating valve is the core technology of the variable thrust regulation of the engine. The flow control of the regulating valve is to use the servo actuation system to adjust the cross-sectional area of the valve to control the entrance pressure of the regulating valve. According to the analysis of the nonlinear factors of the liquid flow test bench and the servo actuation system, the controller algorithm is designed on the basis of the obtaining the equivalent model of the control system through the experimental data method. The effectiveness of the closed-loop control method is verified by the hardware-in-the-loop simulation platform. Meanwhile, it is used in the closed-loop test of regulating value liquid flow pressure.