To study that the effect of gimbaled seeker disturbance rejection rate on the stability of guidance system, the models of the disturbance rejection rate transfer function induced by different guidance signal extraction points and disturbance torque types and the proportional navigation guidance system are established. The uniform asymptotic stability conditions of the guidance system are analyzed by the passivity approach of the Lyapunov stability theory for the timevarying system. Based on the stability condition of the guidance system, the calculation method of the amplitude index of the disturbance rejection rate is proposed. The research shows that when the guidance signal is extracted from the rate gyro, the constraints on the terminal guidance time and the amplitude index of the disturbance rejection rate are more stringent than those from the stabilized loop instruction. The amplitude index of the disturbance rejection rate due to the spring torque is harsher than that due to the damping torque. In the seeker test, attention should be paid to the amplitude index of the disturbance rejection rate caused by extracting guidance signals from the rate gyro and the spring torque.