How to assess the image quality is one of the most important problems in image fusion. By analyzing the existent assessments of image fusion quality,a novel assessment of image fusion quality based on structural similarity is presented. According to different cases,average structural similarity,weighted average structural similarity,product of structural similarity and mutual information are introduced to assess image fusion quality as the objective methods. This assessment considers the structural information of image and the characteristics of human visual system,and can be used to choose the best algorithm in image fusion applications. The experiments of different kinds of image fusion algorithms demonstrate that it is an effective assessment of image fusion quality.