The mode conversion technology is one of the key technologies of the mode division multiplexing, which can realize the transformation between arbitrary optical modes. Moreover, it is the basis for the realization of channel access, switching and multiplexing. A spatial light modulator is used to achieve different mode distributions. The algorithm to generating phase hologram for mode conversion is improved based on spatial light modulator. By using the adaptive simulated annealing algorithm with graphics processing unit parallel computing, a more than seven fold increase in the computational efficiency of the simulated anealing algorithm is obtained. Finally, a mode conversion platform is established, and the experiment is carried out to prove the effectiveness of the proposed method.