Abstract: Historical river system is the artificial water network formed through a long-term dynamic adjustment of the natural process. Summarizing the historical experience has reference meaning to relieve the contemporary rainwater of town, the water resources utilization and the identity crisis.This paper takes typical historic river system of town located in high mountain plains as the research object,focuses on the characteristics of its organizational structure, extracts the “source-sink-flow” structure of the whole river system, and further elaborate three building elements of“source”,“sink”,“flow”. It summed up that the “source-sink-flow” river system structure is a multifunction sustainable river structure with storage, drainage, landscape construction and other functions. Thus, it provides the theoretical support for practical application of the current water system planning of mountainous towns.