The multi-band wavelet is a newly developed branch of wavelet analysis and is superior to the 2-band wavelet, in terms of symmetry and smoothness, for their applications. In this paper, we first discuss the basic theory and analyse the transformation properties of the multi-band wavelet. Next, we apply the multi-band wavelet for two applications: (a) reducing remote sensing images and (b) simplifying the digital elevation model (DEM). Two tests were carried out to assess the applications of the multi-band wavelet method. It is noticed that reduced remote sensing, by the multi-band wavelet method, contains much information and achieves a good appearance on structural feature. The result of the simplified DEM data, based on the multi-band wavelet, maintains not only the stable shape but also the digital elevation value transformed as similar to the original one.