The invention provides a reliability evaluation method for a high-penetration-rate active power distribution network based on a state transition sampling method. The reliability evaluation method comprises dividing the high-penetration-rate active power distribution network into two state subsets of a power generation system and a power distribution system according to different states of elements in the system; evaluating reliability of the power generation system according to different charging/discharging strategies of storage batteries, wherein the charging/discharging strategies of the storage batteries include a load following strategy and a cycle charging strategy; analyzing the state of the power distribution system; and collecting statistics of each reliability index of the power distribution network. The method of the invention calculates the reliability index of the high-penetration-rate active power distribution network by taking capacity constraints of an upper-level transformer substation and power generation and distribution reliability indexes into account, therefore the problem that the reliability evaluation of the power distribution system of the high-penetration-rate distributed power supply is complex and tedious is solved, and the evaluation effect is more comprehensive and accurate; meanwhile, the transition sampling method, which takes the whole system as the sampling object, is used instead of a state duration time sampling method, which takes elements as the sampling objects, so that operation speed is improved and memory usage is reduced.