The application of unsteady simulation to lightening urban storm waterlogged disaster involves six blocks :the main program, the database of drainage networks, the abstractions and losses block, the calculating inflow of sewer block, the drainage networks routing block and the waterlogged areas calculating block. This model can be used forsimulating sewer surcharge and calculating area and water depth of waterlogged areas under storm conditions. The best design of rebuilding storm sewer system or combined sewer system can be provided by simulating existing state of built drainage pipeline. The model was used for rebuilding Shenyang drainage works last year, and the good results were obtained.