The main aim of unwrapping processing is to transform omni-directional images into undistorted ones. An improved unwrapping processing method is brought forward based on forward mapping and the imaging feature of hyperboloidal catadioptric panoramic vision system. Firstly, the pixels of the omni-directional images are mapped to the virtual observation plane, and then unwrapped image is restored by using the modified Shepard scattered data interpolation method, which avoids distortion induced when interpolation is applied in the omni-directional image directly. The experimental results indicate that the improved method is an effective cure for the nonlinear distortion of omni-directional images as well as effective promoter for the smoothness of gray surface and precision of interpolation, bringing more natural result.