In this paper, the models, the methods, and their application experiences of a practical GIS based computer decision-making support system of urban power distribution network planning with seven subsystems, termed CNP, are described. In each subsystem there is at least one or one set of practical mathematical methods available. Some new models and mathematical methods have been introduced. In the development of CNP the idea of cognitive system engineering has been insisted on, which claims that human and computer intelligence should be combined together to solve the complex engineering problem cooperatively. Practical applications have shown that not only the optimal plan can be automatically reached with many complicated factors considered, but also the computation, analysis and graphic drawing burden can be released considerably.