According to the properties of the cross-over between the general canal and the rivers，the layout of the general canal and the flood characteristics，a 2D flood routing mathematical model is established. This mathematical model has applied for the general canal of a large water transfer project with seven crossing rivers located its left side and the flood routing with the 300-year frequency flood is calculated. Key techniques including coordinate transformation, grid generation, numerical separation, treatments of movable boundary and dry land, visualization of calculated results are studied and introduced. And the pictures of the flood routing are demonstrated by visualization of calculated results.The characteristies of water level in each river lying to the left side of the general canal are analyzed, and calculated data for the design of the water transfer project are offered.