Abstract: In the PID parameters tuning problems,the object of model parameters will often change in certain extent.Aiming at this problem,the minimum maximum principle of PID parameters tuning method was proposed.An improved genetic algorithm as outer search method and a simplex optimization lining optimal method were adopted.The genetic algorithm adopts elitist strategy,arithmetic crossover and improved adaptive Gaussian mutation operator.The results show that the controller designed by the proposed algorithm is effective and feasible.The design improves the global convergence,the convergence speed and the robustness of the system.