Abstract: The finite element analysis of 3D simulation for the large-scale canal project during construction period is performed based on the improved node virtual flow method to solve seepage with free surface, and the water head distribution, saturation line, leakage with hydraulic slope are obtained. The emphasis is placed on the study of different precipitation schemes during construction period and the relationship between the quantity of the dewatering well, the underground water level of the canal and the seepage discharge controlling the water level of the dewatering well. The study indicates that the method can simulate the seepage field of canal project well and accurately determine whether the program meets the requirements of the project, and it can give a theoretical and technological support for similar practical engineering.