Abstract: This paper firstly proposes the phenomena that the diameter of particle image obtained is larger than usual with the increase of aperture stop diameter in short object distance image acquisition in PIV measurement which was called spherical aberration. Then the solution was acquired directly by resolving the non-line formula of image acquisition through one positive thin-lens and the relation between the aperture stop and the spherical aberration was computed. Finally the ideal particle image could be acquired by making use of spherical aberration properly in the aim of sub-pixel calculation in PIV and the analysis was also proved by actual experimental results.