Abstract: As a new type of power electronic device,flexible multi-state switch（FMSS）can partly replace the traditional tie switch in the distribution network to realize uninterrupted flexible regulation of power flow and optimize voltage profile.Several possible topologies and working modes of the three-port FMSS in the distribution network are discussed.The dynamic mathematical model of three-port FMSS is established and a three-port FMSS coordination control strategy based on finitecontrol-set model predictive control（FCS-MPC）is proposed,which has many advantages of clear principle,simple implementation and fast dynamic response.It avoids the problems of traditional propontional-integral（PI）double closed-loop control strategy including complex control structure,more PI parameters and difficult setting.Based on FCS-MPC,the control algorithms of UdcQ mode,PQ mode and Uacf mode are implemented.Accordingly,the coordination control strategy between the modes of three ports is presented.In order to verify the feasibility of the proposed scheme,a three-port FMSS simulation model is built by using MATLAB/Simulink.Simulation results show that the proposed coordination control strategy can effectively achieve multi-port coordinated control and adjustment function which can provide a flexible solution for the applications of multi-port FMSS.