Abstract: For the control of non-minimum phase systems,there is a need to solve the problem of tradeoffs between undershoot caused by unstable zeros and settling time.Considering the coupling of undershoot and settling time and the relationships between unstable zeros and undershoot,the control process is divided into undershoot eliminating stage and input tracking stage,and the number of unstable zeros is changed in proper time.The different parame-ters of the controllers in the two stages are optimized with genetic algorithm.Simulation results show that the undershoot is mitigated significantly and the settling time is shortened with the proposed control method,proving the effectiveness of the proposed control method.