Abstract: These fusion methods such as IHS transform, Brovey transform and principal components transform could merge two optical image data of different resolutions—a high spatial resolution panchromatic image and a low spatial resolution but multispectral image. But these fusion methods required the spectral response range of the high spatial resolution panchromatic image was same equal or approximate to the spectral response range of the multispectral image. This paper puts forward a kind of new fusion method called directional filter fusion (DFF) that could merge two optical image data of different spectral characteristics. This paper proposed its algorithm, firstly filtering on the panchromatic image, and then fusing the remote sensing data applying IHS transform. The classification precision by DFF is much higher at spectrum preservation than that by IHS transform.