The invention relates to an algorithm for fusing a multi-focusing image based on salient region extraction. The algorithm comprises the steps of 1, performing GBVS algorithm to obtain salient images of two source images; 2, performing binaryzation for the salient images, and respectively calculating the space frequency so as to obtain space frequency maps; 3, detecting the weak side edges of the space frequency maps by the watershed algorithm to obtain closed areas, classifying, comparing the space frequency of different regions to find out the false focusing areas, filtering the false focusing areas, and processing the rest regions by the morphological method to obtain a focusing area; 4, directly fusing the source image focusing regions, performing Shearlet conversion for the out-of-focus regions, and decomposing to obtain high frequency and low frequency sub-band coefficients, and respectively performing conversion and fusion based on PCNN and laplacian pyramid; 5, reconstructing the fusion coefficients to obtain a fusion image. With the adoption of the algorithm, the gray levels are dispersedly distributed, the image textures are rich, and the details are salient.