DC voltage is an important indicator in measuring the power balance of a DC grid. A large disturbance in system power makes the DC voltage seriously deviate from the rated value. Droop control can realize multi-point DC voltage control, and this is the main means for coordinated control of the DC grid. In order to deal with the DC voltage deviation exceeding the safety threshold after the failure of a single converter station in a DC network, this paper optimizes the design of the gain parameters of the DC grid droop control. It considers the capacity limit of the converter station in the DC grid. Different droop controller coefficients are given based on the rectifying converting operation modes of the converter station. The power distribution of each converter station is optimized to achieve the goal of reducing the deviation of the DC voltage. The superiority of the proposed different gain coefficient methods over traditional methods is demonstrated. The two methods are simulated and verified using the PSCAD. Simulation results show that the proposed method can regulate the DC voltage in the case of large power loss and overflow in the DC grid. The effect is better than traditional methods. This work is supported by the Science and Technology Project of the Headquarters of State Grid Corporation of China (No. SGTYHT/16-JS-198).