To realize the orderly start of the fixed DC voltage terminal, the fixed power terminal and DC Solid State Transformer (DCSST) terminal of three-terminal Flexible DC Distribution System (FDCDS) using star-type structure, the start control strategy of the DC distribution system is designed, and the stop control strategy that power of the power controllable terminal decreases according to the set slope is designed. A coordinated control strategy for the FDCDS is proposed. When the different components on the low-voltage side of the DCSST are switched, the energy storage device is used to suppress the power fluctuation to achieve smooth switching of the components. Finally, through RTDS simulation, the results show that the proposed control strategy can achieve the orderly start, coordinated running and smooth stop of FDCDS. This work is supported by National Natural Science Foundation of China (No. 51777077).