Abstract: Three dimensional design has become the development trend of coal preparation plant engineering design,but it is still lack of special 3D design tool for coal preparation industry in China. So secondary development of the current common 3D design software is needed. Using development language VB,The secondary development of the Solid Works is made,in which the model size can be real-time changed according to the calculated parameters of those buildings and structures in the industrial site of the plant. In addition,the methods of variable design and three-dimensional modeling of design diagram are tried. The results show that the variable design method can simplify drawing steps and improve design efficiency.