Facing the rapid change of structure and scale of distribution network, this paper presents an improved minimal path method for distribution networks based on GIS Data to analyze the reliability of actual complex distribution networks accurately and rapidly. In this method, a complete set of simplification of network topology data, construction and equivalent transformation of minimal path matrix, process of calculating distribution networks reliability is designed to achieve the calculation of massive complex distribution network reliability based on GIS topology sheet. This method simplifies distribution network structure by eliminating component, and reduces total components in searching by extracting components selectively. This method achieves directed search from buses to distribution transformers by adjusting topology data in the process of search.The feasibility and accuracy of this method are illustrated by contrasting the calculation results of the improved method and traditional method on an actual distribution network.