To address a transient overvoltage problem caused by DC blocking faults, an optimization strategy of the excitation system control parameters of the condenser is proposed. First, a transient voltage influence factor is introduced to quantitatively analyze the influence of the reactive power output of the condenser on the transient voltage under a DC blocking fault, and based on the transient characteristic analysis of the condenser, the influence mechanism of the excitation system control parameters on the transient reactive power output of the condenser is clarified. Secondly, the quantitative relationship between the dynamic reactive power output and transient overvoltage of the condenser under a DC blocking fault is established, and the relationship between the transient reactive power output of the condenser and the excitation control parameters is quantitatively analyzed. An optimization strategy of the excitation system control parameters for suppressing the overvoltage is put forward. This can realize deep mining of the condenser’s transient reactive power regulating capability under a DC blocking fault. Finally, an AC-DC hybrid system with a condenser is constructed on the PSCAD simulation platform. The simulation verifies that the proposed excitation parameter optimization strategy has good transient overvoltage suppression capability.