Based on characteristics of longitudinal water level and channel regulation project in reservoir reach of Naji junction, this paper establishes the orthogonal curve two-dimensional current mathematical model for the reservoir tail reach, and analyzes the channel regulation effect for the reservoir reach according to materials of the design stage, acceptance stage and topography after 3 years of completion, as well as the calculation results by mathematical model. The analysis shows that construction site is consistent with the design; the channel dimension and curvature radius of the waterway conform to the design dimensions’ requirement; no siltation occurs 3 years after completion, and the elevation of the unexcavated area is lower than that of the excavated area. In a word, the channel regulation effect meets the design goal.