The District heating system (DHS) can effectively save energy, so it has been widely used and promoted on a global scale. There are still a series of problems. In order to improve the problem of high energy consumption during transportation, it is necessary to study the hydraulic characteristics of DHS. Through the survey of OHS in different cities, it was found that the form of the heating network was toward a loop pipeline network (LPN) with multiple heat sources. Previous hydraulic models of the dendritic pipeline network (DPN) were expressed. As for LPN with multiple heat sources, deficiencies of treatment were analyzed. It was pointed out that LPN with multiple heat sources was a spatial network. Graph theory was applied to the establishment of the spatial network. And the hydraulic model of LPN with multiple heat sources was established. MKP was used to solve the mathematical model. The actual engineering case was used to verify the accuracy of the model and its solution method, which provided a theoretic and practical basis for the study of the hydraulic characteristics of the DHS. (C) 2011 Elsevier Ltd. All rights reserved.