Gabor on-axis digital holography is suitable for the situation that light transmission energy is much more than the energy blocked by the target. Therefore, the reconstruction study on the small target at different lateral positions has important application value. The experiments on 2.52 THz Gabor on-axis holographic imaging at different lateral positions are conducted, the Tukey window function and the angular spectral method are combined to realize two-dimensional reconstruction, and the results are compared and analyzed. The experimental results show that the algorithm proposed inhibits the aperture effect and also improves the contrast ratio of the whole image. The reconstruction performance of the target close to the central position of the detector is slightly better than that near the edge.