Using the two-dimension mathematical model of long river section between Zhuzhou and Xiangjiang hydro-junctions,the paper studied the variation feature of water surface curves in the area of Changsha hydro-junction and analyzed the influence of reservoir operation on navigation water depth in reservoir area.According to the design scheme, it determined the control scheme of submerged scope in the reservoir area of Changsha hydro-junction,and calculated the reservoir control line of submerged curve,and derived the relation between storage water level and flow of reservoir controlling section (Xiangtan hydrological station) and reasonally determined the pre-discharge water level scheduling line so as to offer the boundary constraint conditions for the subsequent reservoir optimization operation.