Abstract: In order to remedy the limitations of Autodesk Civil3D in the design of water and soil conservation projects, and solve the traditional spoil area design problems, such as lack of professional auxiliary design software, low level of informatization, and difficulties in 2D and 3D design conversion, we adopt the method of secondary development of Civil 3D platform with C# language, Winform interface development, Civil 3D API and Subassembly Composer and MVC architecture mode.By analyzing the business process of each design step of the spoil area, a professional platform suitable for the design of the spoil area of water and soil conservation project is developed, which can realize the functions of slag capacity analysis, stability calculation, rapid modeling and mapping calculation.The platform has been successfully applied in the design of multiple spoil areas in water supply project of transferring water from Taohe River.The results showed that the platform associated the engineering design specifications with the visual operation interface of step guidance, which greatly improved the design efficiency and design quality while made up for the lack of professional auxiliary design software in the design of spoil areas, and effectively promoted the transformation of the design of spoil areas from two-dimensional to three-dimensional.