This paper proposes a novel omni-image Interpolation technique and a new method to evaluation its performance. Omni-images are taken by non-linear catadioptric camera and offer important scientific and engineering benefits but often at the expense of the reduced visual accuracy. Interpolation algorithms aiming at improving the resolution of omni-images are deemed as an effective approach to deal with such a lack of visual content. Main contribution of this paper is that we propose an interpolation algorithm which could not only enhance the visual quality but also maintain camera parameters. Camera properties of the interpolated images are preserved by utilizing the epipolar geometry constraint of non-linear images. In our experiment, good performance was found on four sets of omni-images using the proposed method compared with the standard bilinear algorithm and bicubic algorithm.