Based on the study of Wanquan river navigation channel first phase construction, we established the orthogonal curve 2D current mathematical model for the reach from Jiaji to Bo’ao in Wanquan river. Firstly, the model was verified with the nature current materials, and the calculated result was consistent with the nature data by adjusting some parameters. Using results of simulation the spring tide and neap tide in dry season as well as spring tide flood season, we analyzed the variation characteristics of underwater topography, water level and gradient ratio along the river reach. The variations of the tidal limit and tidal current limit were displayed. The specific location of tidal reach was given. Finally, 2D plane flow field about Bo’ao reach was analyzed. The results provides a technical support for the navigation channel construction of Wanquan river.