The main cable is made of PPWS. Its large displacement and nonlinear mechanical properties are shown by their own elastic deformation and its geometry changes affecting the system balance. To get the real main cable-shaped of long-span suspension bridge, based on the finite element method, the element stiffness matrix was derived, which displacement field was same to the element shape. Then through the horizontal and vertical direction equilibrium equations were solved, the relationship between main cable shape and the system parameters was obtained. The calculation method was compiled to MATLAB 7.0 programs, and applied to ascertain the main cable-shaped of one long-span suspension bridge. When the paper calculated result was contrasted with the design value, it could be concluded that: the main cable-shaped of long-span suspension bridge could be accurately obtained by the paper method, and the method was convenient for compiling.