The damage effectiveness of a Multiple Launch Rocket System (MLRS) is highly sensitive to deviations in launch angle, making it necessary to rapidly eliminate angle deviations of the yaw body and pitch body during salvo firing. This paper designs a Linear Quadratic Regulator (LQR) to eliminate angle deviations and calculates the angle deviations caused by the dynamic response lag of the actuators. The study begins by establishing linear dynamic equations for the MLRS chassis, yaw body, and pitch body using Lagrange formulation. Subsequently, an LQR is designed with the yaw angle and pitch angle as state variables and torque as the control input, capable of regulating terminal error, operation time, and control input. Simulations are conducted for the angle deviations caused by the salvo firing of four rockets, yielding the desired torque and desired rotational speed. Permanent Magnet Synchronous Motors (PMSMs) serve as the actuators for the yaw and pitch parts of the MLRS. To compute the angle deviations resulting from their dynamic response lag, the PMSMs are commanded to track the desired torque, thereby obtaining the actual torque and rotational speed of the yaw and pitch parts. The results demonstrate that the LQR designed in this study can eliminate no less than 98% of the angle deviations within the firing interval.