Volumetric 3D display is a technology for displaying stereoscopic graph in space. The technology is presented in brief. The spatial coordinate transformation problem in it is discussed. By approximating and inducing the actual problems existed, the corresponding geometric optical problems are obtained. Then, they are solved in detail and the relative parameters for experimental measurement are designed. Finally, relative algorithms are designed according to the solutions and the corresponding experiment is carried out. The result shows that the correctness and effectiveness are verified.