Abstract: To investigate the dynamic response of chamber pressure during mode-switching of divert and attitude control motors, a pressure-feedback control scheme was adopted. Combined with zero-dimensional internal ballistic and valve servo modeling, the open-loop pressure response was simplified as a first-order inertial element, which was further reduced to a standard second-order system upon the application of closed-loop control. Analytical formulas were derived to describe the dynamic effects of motor characteristic parameters on the mode-switching process, as well as disturbance control errors, and steady-state errors under constant, linear and sinusoidal disturbances were analyzed. A pressure feedback control test was designed, where multiple types of disturbances were generated by adjusting the opening of the attitude control valve, and two groups of mode-switching verification tests were implemented. Test results reveal that proportional control can eliminate errors induced by constant disturbances, but constant offsets persist under linear disturbances and identical-frequency errors occur under sinusoidal disturbances. The dynamic response exhibits obvious time-varying characteristics when mode-switching is triggered at different operating moments. With the target pressure of the high-pressure mode set to 9 MPa, the open-loop gain is increased via control parameters tuning. The control error is limited to 0.2 MPa across all stages without disturbance injection. After introducing various disturbances, the maximum control error reaches 0.5 MPa and the maximum mode-switching time is 0.8 s, which proves that the system possesses strong disturbance rejection capability.