Abstract: Image fusion method based on wavelet transform and block segment of the images is proposed.An immune particle swarm optimization search algorithm is developed for fusion of two spatially registered multi-focus images.In order to get the optimal image，the size of block is defined as particle.Two evaluation criteria such as information entropy and cross entropy are used on the analysis and effect evaluation of different fused images.The performance of this method is better than the performance of the existed fusion method.It can eliminate the blocking artifacts of the fusion image and save the time of fusion.The experiment results show that the method is an effective method.W-PSO is tested for performance comparison with IPSO，and the result show IPSO has the higher efficiency than W-PSO.