The invention discloses a fault distance detection method for an active power distribution network, and the method comprises the following steps: first, obtaining the data of an active power distribution network; second, determining each power supply section so as to confirm the troubled section; using the forward-backward sweep method to calculate the injection current of the downstream of the troubled point to the troubled point; calculating the voltage phase amount and the current phase amount at the downstream end of the troubled section and calculating the nominal position of the troubled point; and finally calculating the distance from the troubled point to a transformer substation. In the method of the invention, the distribution-type power supply multi-point accessing is considered, and only through the use of the local voltage and current phase amounts and the synchronous current phase amount of the distribution-type power supply, it is possible to realize the fault distance detection for the active power distribution network. In addition, through the comparison of the current at the two sections of an area section, the positioning of a troubled area section can be realized. Through the calculation of the fault current and the contribution of the downstream current of the fault point to the fault current, the positioning and distance detection for the fault can be realized, making the method suitable for the fault distance detection under the condition of a multi-point distribution-type power supply accessing.