Abstract: Multispectral image is interpolated in each band using Poisson equation with panchromatic image as guidance based on the known condition.The resulting multispectral image keeps most spectral information of original one and possess clear details as the same as panchromatic image.The method works without limitation of band quantity and association with Multigrid solver improves efficiency of data processing.The values of quality index on RASE,ERGAS,spatial detail and SSIM of the proposed new method do well or better compared to traditional image fusion ones in experiment on QuickBird and IKONOS images.