This paper presents an algorithm of locating single-pole-to-ground faults in DC distribution network based on power flow calculation. The fault current feature flowing through fault point is analyzed, implying the pole-to-ground voltage at the fault point of fault pole is almost zero when the transient process ends. Given this precondition, the distribution of residual voltage of each measuring point in fault pole can be calculated with the load current, which is obtained by power flow calculation. By comparing the similarity between the distribution and the measured residual voltage distribution in real fault, the node which makes the maximum similarity is identified to be closest to the real fault point. An impedance-based method is applied further to calculate the accurate location of fault point. Simulation model is established based on Matlab/Simulink, and the test results demonstrate the validity of proposed algorithm.