Based on the characteristics of high-voltage direct-current（HVDC）system feeding into a weak AC system，optimization of the DC control and protection systems of Qinghai-Tibet±400kV HVDC project has been developed.The strategy of low DC voltage start and stop sequence is used to decrease the impact of impulse on the Tibet grid.The reactive power control strategy coordinated with static var compensator（SVC）is used to restrain the voltage fluctuation while connecting or disconnecting filters.The power transfer method based on DC voltage step is used to solve the power compensation problem when DC voltage is below280kV.Cooperation with stability control equipment by continuous power modulation，fixed criterion of DC line under-voltage protection and restart logic optimization are also proposed by continuous power regulation.Simulation and practical results indicate that the proposed optimizations are effective.