Flexible multi-state switch（FMSS） is a new type of power electronic device which has the function of power flow transmission and voltage support. In order to realize the potential of FMSS reasonably

multi objectives may be taken into account during the operation optimization. Therefore

we propose an operation optimization model of the distribution network with FMSS

in which. the power of FMSS

the action time

and on-off state of the conventional switches are taken as optimization variables of the model. The model contains two sub-problems

network reconfiguration and FMSS regulation

and can be solved by the idea of bi-level programming model. Scenario tree is used to simulate the output of the distributed generation（DG）. Based on the divided time interval of network reconfiguration

time of network reconfiguration is optimized. Using the strength Pareto evolutionary algorithm

the Pareto optimal solution set of network reconfiguration and FMSS output is solved. Moreover

the final operation method is selected by membership function. Based on improved IEEE-33 bus distribution network

validity of the operation optimization algorithm is verified. The results show that the operation optimization method can be adopted to improve multi operation indexes and works well under a series of DG penetrations.