The current characteristics at fault occurrence time in active distribution networks are studied, based on the principle of polarity check of current transformer, a fault location algorithm for active distribution network based on polarity check is proposed in view of network topology parameter of the distributed feeder automation. This algorithm checks the isonym end of topology polarity and wiring polarity in distribution network topology in the network topology and isonym end of polarity check, generates fault location topology coefficient matrix, and locates fault according to the current waveform of fault occurrence time and fault location topology coefficient matrix. An intelligent distribution terminal with intelligent distributed feeder automation based on the fault location algorithm is developed and is simulated and verified by RTDS, the results show that the fault location algorithm based on polarity check in active distribution network system can accurately and effectively carry out fault location without relying on voltage transformer.