The invention relates to a voltage control method applied to a flexible DC power distribution network, which belongs to the technical field of DC power distribution system voltage control. According to the method, a master station adopts constant voltage and constant reactive power control, the master station serves as a slack bus to control system DC voltage, a voltage reference value is provided for the overall DC power distribution network, and when an AC system fails, reactive power support is provided for the AC side. A slave station adopts a P-U-I controller; when the system operates in a steady state, a converter station VSC is in a power control mode PQ, the power is adjustable, the voltage is controllable, power ring control P adjusts output of the VSC according to a system power optimization instruction sent by an energy management system EMS and distribution network power flow is optimized. When the system is in a transient state, the VSC is in a VdcQ mode, voltage ring control U maintains system DC voltage, and the system operates in a rated voltage upper limit and a lower limit. The voltage control method applied to the flexible DC power distribution network has the advantages that the structure is simple, gradation is distinct, realization is easy, the hardware communication cost is greatly saved, system control is simplified, and adaptation and expandability are wide.