Stationary multi-consensus and convergence performance optimization of multi-agent systems via rectangular wave controller are studied. Firstly, a rectangular wave control protocol is designed with adjustable action time, and a necessary and sufficient condition of multi-consensus problem is given based on Hurwitz stability criterion. Then, a parameter optimization algorithm is designed for the faster multi-consensus convergence rate via the dichotomy,and the minimum spectral radius of the multi-agent system is taken as the optimal index in the algorithm. Finally, a numerical simulation is given to show the effectiveness of the rectangular wave control protocol proposed in this paper. These results show that if the suitable parameters of the rectangular wave control protocol are given, the multi-agent systems not only can achieve stationary multi-consensus, but also can improve the convergence rate greatly.