Techniques of programmable vertex shader and pixel shader have been integrated in newly developed graphics hardware armed with powerful Graphics Processing Unit(GPU) in recent years, and as a result, real-time volume rendering can be implement. First, rendering pipeline, hardware architectures on per-pixel shading and fast rendering principium of the modern programmable GPU are explained in detail. Second,technology on how to analyze and solve volume rendering problems is described. Finally, maximum intensity projection (MIP) method rendering medical volume data have been implemented based on programmable Graphics Processing Unit. In a performance test, spent time rendering medical volume data based on programmable pixel shader in GPU is obviously less than spent time rendering it do without programmable pixel shader.