Abstract: The application of GPGPU model of NVIDIA in dose calculation based on CUDA program technique was studied. It was the first time that GPGPU method was used in commercial 3D radiation therapy planning system based on point kernel convolution/superposition model. The old dose calculation model was modified in order to make it be used in device for the parallel computing. At the same time the MFC DLL and export class technique was used to avoid mass code migrating work. The most efficient number of parallel threads was determined by analyzing the result data. The results showed that the dose calculation speed is improved remarkably and the single beam computing time is less than one second using GPU speedup method, which improved the competition ability of the product.