Augmented reality is the merging of synthetic sensory information into user's perception of a real environment. One of the most important tasks for every augmented reality application is to merge the virtual scene and real scene correctly and make it be an organic whole. Based on the analysis of 2D planar augmented reality application, the application of image analysis technology in virtual-real registration is investigated. A numerical background expression method is put forward to facilitate the feature point extraction in the virtual-real registration process.