The fault transient of multi-terminal DC power grid develops very fast, so it is necessary to configure current-limiting reactor to restrain the rise of fault current in practical engineering. However, the configurations of current-limiting reactor will also impact on non-fault part while limiting the fault current. Therefore, configurations of current-limiting reactor in multi-terminal HVDC transmission system are studied in this paper. Firstly, the fault calculation model of multi-terminal DC transmission system is established, and the calculation method of system state quantity including each action stage of circuit breaker is given. Then, this paper analyzes the problems that are considered in the configuration of a current limiting reactor in multi-terminal HVDC transmission system. Finally, taking four-terminal HVDC transmission system as an example, the fault process of the DC system under different current-limiting reactor configurations is simulated and calculated. Based on the calculation results, the influence of current-limiting reactor on the maximum fault current, the blocking condition of converter station, overvoltage of DC bus and decay time of over-current of a system is analyzed.