Abstract: In this work, we implement the traditional ray-casting-based volume rendering algorithm on the programmable graphics processing unit （GPU）.By the algorithm,at first the volume data is transferred into the video RAM as 3D texture, then the ray’s entry point, leave point and the ray traversal in the GPU are calculated by the vertex program and the fragment program.Finally, different rendering effects are achieved according to various blending functions of the sampling points.Our implementation only needs to render one quadrangle for 3D reconstruction.The experi ment shows that when reconstructing with shading effect, the GPU-based ray-casting algorithm can meet the requirements of real-ti me interactive rendering, and it can also realize so me complex effects such as translucency.