Abstract: Mechanical resonance usually occurs in a large-scale radar control system,It is difficult to overcome the resonance by method based on classical control theory, In this paper, a new design method based on modern control theory and observer theory is presented, and is used in designing a practical large-scale radar control systern, The results of simulation show that the mechanical resonance can be overcomed by applying the method. In addition, the method offers a efficient way of improving tracing and anti-disturbance ability.