The invention relates to a state labeling method in the field of electrical power systems, in particular to a power distribution network reliability assessment state labeling method based on segments. The state labeling method is characterized by being based on the segments and combined with transferring supply after a distribution network faults, enumerating the faults in each segment, conducting state labeling on all segments and internal elements of the segments according to the faults in each segment, and saving labeling results in a vector data structure corresponding to a fault segment. The state labeling method comprises the following steps of (1) conducting reliability assessment state labeling pretreatment based on the segments; and (2) calculating reliability indexes in a circulated mode. The number of the segments in the power distribution network is fewer than that of feeder segments, so that search based on the feeder segments is only carried out when first depth search is carried out, then transversal is carried out on all segments according to the faults of each segment, a complex process that each feeder segment fault traverses all feeder segments is avoided, and the state labeling method is high in efficiency.