Abstract: A numerical test on the accuracy of the particle image velocimetry is conducted.It is assumed that the information of the particle image photographed by double-exposure with a light sheet is processed by correlation method.In order to study the effect of non-uniformity of fluid motion on determination of the velocity vector at an interrogation spot,five typical non-uniform factors are discussed.A statistical method is used to get quantitative estimation.The results suggest that the accuracy of this PIV method is significantly affected by some factors of non-uniform flow.