Abstract: Based on the results given in 5, the main results presented in this paper are as follows:1. The controller gain is reduced to a minimal degree as possible to overcome the drawback of “conservative” in the design of robust controller; 2. The sufficient conditons and related computational results are given for the existence of designing of robust controller; 3. The procedure for designing a robust controller is presented in considerable detail. Furthermore, a illustrative example is also given to demonstrate the simplicity and effectiveness of the proposed method here.