In the constant-color background, the structure feature is more influential in evaluation of the target camouflage effectiveness its surface is covered by the color that matches the background compared with the color feature. Against this, a method fusing the index of similarity and the index of difference is proposed. The index of similarity is designed based on texture, orientation and intensity features and described by saliency maps. The index of difference is designed based on target’s own feature of straight-section edge and described by the weighted maximum entropy principle. These two features are fused to evaluate the camouflage effect. Experimental results show that our camouflage evaluation framework accords with the human visual perception mechanism.