To solve the problem of spectral distortion in remote sensing image fusion, an improved transform method based on midway image equalization was proposed. First, the multispectral image was decomposed by IHS (Intensity, Hue, Saturation) transform; then by using the midway image equalization, the cumulative histogram of panchromatic image and the spectral intensity component of multispectral image were adjusted to be the same; finally, the inverse transform of IHS was implemented and a high quality fusion image was obtained. The theoretical analysis and experimental results show that the proposed algorithm can not only suppress the spectral distortion of the fusion image, but also preserve the spatial resolution of the fusion image effectively, and it is simple and easy to implement. Compared with the traditional fusion algorithms such as IHS transform, Principal Component Analysis (PCA), Wavelet Transform (WT) and Brovey, the fusion images generated by the proposed algorithm have good visual effects; in addition, the proposed algorithm has better performance in terms of Peak-Signal-to-Noise Ratio (PSNR), spectral distortion and information entropy. Fusion images obtained by midway image equalization maintain spatial information well and have little spectral distortion.