The invention relates to a fault locating method and system of an active power distribution network. The method comprises the following steps that 1 fault current constant values of feeder terminals are set to be higher than the largest load current; 2 when the active power distribution network has faults, fault detection is started for the feeder terminal through which a fault current passes, and a short-circuit current measurement value is submitted to a power distribution network system master station; 3 the power distribution network system master station resets a fault current constant value according to the short-circuit current, passing through an outlet breaker, submitted by a circuit outlet switch feeder terminal and then judges whether the fault current passes through a switch of one certain circuit, and the fault section is recognized by adopting a common fault locating method. The system comprises the power distribution network master station, the feeder terminals and a communication system, and the power distribution network master station is connected with all the feeder terminals through the communication system to achieve information exchange. The method and system can locate the faults easily and rapidly, easy to achieve and good in use effect.