Abstract: Most of fusion algorithms at present such as IHS method,Brovey method,PCA method,wavelet transformation,Gaussian-Laplace pyramid are operated under certain fusion rules,and cannot be adjusted adaptively according to the application target of the fusion images. In order to solve this problem,data assimilation conception in meteorological field is introduced and a novel method fusing multispectral and panchromatic images based on the data assimilation is proposed. The method can adjust the values of the image quality evaluating indicator according to different using goals.