Abstract: An improved registration method of multimodal images combined optical flow and Speeded-Up Robust Features (SURF) is presented in this paper. As a noteworthy limitation, the traditional registration methods based on optical flow are not suitable for the multimodal images with large differences in structure. Firstly, histogram specification is used to transform modal of images before registration, the similar modal of images are beneficial to the following image registration. Then, in order to solve the problem of structural differences in image registration, an improved registration method of multimodal images combined optical flow and SURF is presented in this paper. Finally, the high performance computing technology based CUDA was proposed in this paper. Experimental results show that the measure indexes of our method are more competitive compared with the other methods, which indicate the proposed approach has the higher accuracy and better robustness.