The slag produced during the operation of the burner of the solid rocket ramjet will deposit and fall off at the throat of the burner, resulting in a change in the effective throat area, thereby affecting the flow regulation accuracy. In this paper, the physical process of throat deposition and shedding is analyzed and modeled, and the equivalent deposition area of the throat is polynomially fitted with time as a variable, and a PID controller is designed to regulate the gas flow. The simulation results show that the designed controller can effectively suppress the drastic pressure change caused by the slag deposition and drop in the throat, which provides a reference for the controller design of the actual gas flow regulation system.