The goal of ratio enhancement for hyperspectral (HS) image pansharpening is to obtain an enhancement ratio between a simulated low-resolution panchromatic (Pan) image and an original high-resolution Pan image. However, the simulated low-resolution Pan image often suffers from gray-level distortion. To solve these problems, the original HS bands are synthesized to a smaller number of reduced HS bands, then the pixels of Pan and HS images are divided into different groups according to the linearity between the Pan band and the reduced bands. For each pixel group, a nonnegative least-squares algorithm is utilized to calculate the weights of reduced HS bands, so that the simulated Pan image is obtained by weighted summation of reduced HS bands. Finally, the HS image is sharpened by a ratio enhancement. The experiments demonstrated that the proposed method had a good performance on fusion quality. (C) 2017 Society of Photo-Optical Instrumentation Engineers (SPIE)