The urban storm flood analysis is of great significance to the study of numerical simulation of urban storm waterlogging. In the traditional urban storm flood analysis algorithm, water level of waterlogging is essential for urban storm flood analysis with given water level,but it is difficult to obtain it in real situation; The urban storm flood analysis algorithm with given water volume is simple and has a fast calculation speed,but it also has the disadvantage of the limit of catchment area boundary. To overcome these deficiency, a dynamic diffusion algorithm with source term of water volume in waterlogging is proposed. The algorithm has a high accuracy and avoid the subjectivity of human choice of multi direction influence factors. Taking Longwen District of Zhangzhou as an example, the rainfall in June 15, 2016 was selected to validate the algorithm. The results are basically consistent with the measured results. So a conclusion can be reached that the algorithm is effective and accurate.