Image mosaic in image processing is widely used. However, its key issue is image registration, and clear mosaic from several relevant images with no splicing trace. Therefore,an algorithm is put forward: firstly, gray correlation method is utilized for matching search with image information in wavelet domain, and random sample consensus (RANSAC) algorithm is used to work on match point; Secondly, adaptive filtering is established in the wavelet domain for image flat fell,and the wavelet coefficient matrix is concluded;Finally, wavelet inverse transform on the wavelet coefficient matrix. Experimental results show that the proposed algorithm can finely smooth the seam line on the mosaicking boundary thanks to image mosaic in wavelet domain and adaptive filtering (instant changing filter's form)according to the adjacent two images' own information.