A new data fusion method is proposed in this paper for improving CBERS-1 IRMSS images based on CCD image. After precise co-registration, each pixel in a low spatial resolution image is correspondent with a group of sub-pixels in a high spatial resolution image. For each pixel in the low spatial resolution image, the average value of its co-registered sub-pixel brightness values in the high spatial resolution image was calculated. The difference between the pixel brightness value in the low resolution image and its sub-pixels average value was added to every sub-pixel value in the high resolution image. This procedure was applied to each pixel to produce a data fusion image. The fusion image had more spatial details than the low resolution image, and its spectral information was similar to that of the low resolution image. The test result indicates that the new data fusion method is an improved fusion technique not only in enhancing the spatial details of IRMSS image but also in keeping the fidelity of the image spectral properties. Different from other data fusion methods, the new method can perform data fusion for an individual low resolution image and realize the enhancement of the thermal infrared band 6 of Landsat based on the other higher resolution band image. Being a very simple and practical technique, it is potentially useful in enhancing the spatial details and preserving the spectral fidelity of the low resolution images.