We introduce a new spectrum transform into the image fusion field and propose a novel fusion method based on discrete fractional random transform (DFRNT). In DFRNT domain, high amplitude spectrum (HAS) and low amplitude spectrum (LAS) components carry different information of original images. For different fusion goals, different fusion rules can be adopted in HAS and LAS components, respectively. The proposed method is applied to fuse real multi-spectral (MS) and panchromatic (Pan) images. The fused image is observed to preserve both spectral information of MS and spatial information of Pan. Spectrum distribution of DFRNT is random and uniform, which guarantees that good information is reserved.