The invention provides a reliability evaluation method for an active power distribution network based on switch boundary subarea division. The reliability evaluation method comprises dividing the area containing the active power distribution network into nine subareas according to the installation positions of switches; according to reliability calculating expressions corresponding to different fault subareas, calculating the duration of power interruption, which is caused by a fault point corresponding to a feeder line of a fault, of a load point, the calculation comprising: calculating the interruption fault rate and interruption duration of the fault point in areas without power supply of a distributed power source, and calculating the interruption fault rate and interruption duration of the fault point in areas with power supply of the distributed power source; and measuring system reliability through calculating annual fault interruption rate and annual average interruption time of the load point, specially, measuring system reliability by adopting a system average interruption frequency index SAIFI and a system average interruption duration index SAIDI. The method of the invention reduces analysis amount, can accurately evaluate reliability of the power distribution network containing a distributed power source and provides reliability evaluation basis for development of Chinese active power distribution networks in the future.