A method and a system are provided for generating an on-screen display using 3D graphics in devices without a high quality 3D graphics accelerator. 3D graphic images obtained from a 3D graphic image generator are mapped to 2D graphic images, and the mapped 2D graphic images are moved according to 2D motion vectors estimated from 3D motion of a 3D geometric object on a viewport. Accordingly, it is possible to generate and display a 3D graphic on-screen display.