This paper proposes a fusion method by combining generalized intensity-hue-saturation（GIHS） transformation and maximum a posteriori（MAP） analysis in order to improve the fusion quality of multispectral（MS） and panchromatic（Pan） images from a new type of remote sensing platforms.The intensity component of the MS images is first obtained by GIHS transformation.Then a new Pan image is acquired by combing the intensity component and Pan image using a steepest-descent optimization algorithm based on the MAP framework.Thus

the fused images are obtained by the GIHS method.Experiments are conducted using the IKONOS MS and Pan images

and Quickbird MS and Pan images.The proposed method is compared with the GIHS fusion method

the wavelet transform（WT） fusion method

and the combined WT-GIHS fusion method.The experimental results show that the proposed method can achieve better fusion result than exiting fusion methods.