Objective The image fusion method of wavelet transform has important application value. To explore the influence of different fusion strategies on the effect of image fusion, we choose multi-focus images and standard MRI/CT gray images for source images. Methods For low frequency fusion of multimodal medical image, we adopted the weighted average, the maximum method, region energy and region variance, respectively. For high frequency fusion of multimodal medical image, we adopted the region energy, region variance and neighborhood window filtering with consistency checking, respectively. Results Based on the comparative analysis of fusion image from subjective and objective (gray histogram, edge detection and the performance evaluation) effect, we found the optimal fusion strategy for multimodal medical image fusion. Conclusions The experimental results show that the outline of the fused images is clear and its edge is complete when local variance fusion is selected for low frequency fusion, and that the detail information of source image is reserved and strengthened when consistency checking based on neighborhood window is used for high frequency fusion.