The present invention provides a DC power grid voltage control method. According to whether the converter station has an ability to regulate voltage or not, the converter station is divided into three categories, namely a voltage control converter station, an auxiliary voltage control converter station, and a power control converter station. The voltage control converter station works in a constant voltage control mode or a current limit control mode; the auxiliary voltage control converter station works in an auxiliary voltage control mode, a constant DC voltage control mode or a power control mode; the power control converter station works in a constant power control mode. Through the adoption of the voltage control method disclosed by the invention, the DC voltage and the power can be controlled accurately in a steady state, and the voltage and the power can be stabilized in a transient state.