:A secondorder explicit difference tidal flow mathematical model with triangular grid is set up which can raise the stability and precision of previous triangular grid explicit mathematical model. Employing a new auto triangulation technique to generate triangular mesh, with 'wettingdrying' judging method to handle moving boundary problems and by means of two sets of node relations to treat submerged dyke problem, the tidal flow field of the Oujiang Estuary with large sea area,multiislands, complex topography and flow patterns was successfully simulated and verified by observed hydraulic parameters in prototype. According to the simulation results, the characteristics of tidal flow in the Oujiang Estuary are
analyzed.