Abstract: In order to control the quality of irrigation and drainage, save water and land resources and reduce the cost of saline-alkali soil reclamation, it was necessary to design rationally irrigation and drainage engineering technical parameters. The paper proposed a new method to estimate technical parameters of irrigation and drainage engineering for coastal saline-alkali soil reclamation in Tianjin. It was assumed that soil was a homogeneous and isotropic porous medium, and the depth of flooded water on the surface of the land was very small. Under the condition of flooded leaching and draining, the water flow state can be considered two-dimensional steady. Based on Vedernikov infiltration equation, Van der Molen leaching equation and water balance equation, the solution for technical parameters was established. The proposed method was demonstrates through a case on reclamation of coastal saline-alkali soil by leaching and draining, and the results were more consistent with experience values in practical engineering. The research provided guidance for planning and design of saline-alkali soil improvement in Tianjin.