DC circuit breaker is the key equipment to construct DC power grid, transmission line and converter station can be connnected to DC power grid by closing DC circuit breaker, and the temporary fault of the transmission line can also be recovered by the reclosing operation of DC circuit breaker. In this paper, the hybrid DC circuit breaker is taken as the research object. Firstly, the closing/reclosing principles of hybrid DC circuit breakers are introduced. Then, soft-closing strategy of hybrid DC circuit breakers based on transfer branch group-by-group conduction is proposed, and two kinds of basic transient process of soft-closing strategy are analyzed. Through the analysis on the transient processes of different closing/reclosing applications, it is concluded that the proposed soft-closing strategy can reduce the overvoltage during closing/reclosing operation and realize the converter station starting from the DC side without any pre-change circuit. In addition, a soft-closing overcurrent protection method and energy balance method of energy dissipation branch are proposed to improve the soft-closing strategy, which can effectively reduce the breaking current when closing to fault and the energy imbalance of the energy dissipation branch. Finally, the validity and feasibility of the presented soft-closing strategy, and the soft-closing overcurrent protection scheme and energy balance metho are verified through PSCAD/EMTDC simulation analysis.