Fast calculation of trapping force provides a more direct way for optimizing designs of optical systems which generate optical traps. In this study, a graphic processing unit (GPU), NVIDIA GTX 275, is used to boost the speed of trapping efficiency calculation under ray optics approximation. The codes of trapping efficiency calculation are implemented in C++. The computing power of GPU is utilized through compute unified architecture device (CUDA) toolkit 4.0. The computing speed is compared with that of central processing unit (CPU), Intel Core 2 Quad Q9550. Over 100x speedup is achieved when single-precision floating-point numbers were used in the calculation.