The invention relates to a voltage control method for a DC power distribution network, and a system. The method comprises the steps: determining the switching efficiency of each module in a combined resonant converter according to a configuration strategy of the combined resonant converter, determining the voltage gain of an output side DC bus of each module of the combined resonant converter according to the switching efficiency of each module in the combined resonant converter, and adjusting the voltage of the output side DC bus of each module of the combined resonant converter through the voltage gain of the output side DC bus of each module of the combined resonant converter. The method employs the combined resonant converter, and achieves the stable control and power flexible distribution of the voltages of DC power distribution networks at different voltage levels through simple operation on the basis of reducing the power stress of a power device.