In this paper, design approach of PID controller with rejection function against external disturbance in motor control system is proposed using immune algorithm. Up to the present time, PID Controller has been used to operate for AC motor drive because of its implementational advantages in practice and simple structure. However, it is not easy to achieve an optimal PID gain with no experience, since the gain of the PID controller has to be manually tuned by trial and error in the industrial world. To design disturbance rejection function, disturbance rejection conditions based on H_∞ are illustrated and to decide the performance of response for the designed PID controller, an ITSE (Integral of time weighted squared error) is used. Hence, parameters of PID controller are selected by immune algorithm to obtain the required response.