Eshelby tensor is not a constant parameter and there is no analytical expression for a non-ellipsoidal particle. To simplify the calculation, non-ellipsoidal particle usually was treated as ellipsoidal in most analysis, while the simplification is need to be verificated for particles in composite are not always ellipsoid actually. To study the error of the simplification, the Eshelby tensor and the average Eshelby tensor of several non-ellipsoidal particles were calculated numerically, and the numerical result is verified by comparing to the finite element method result. Base on the numerical result, the influence of the non-ellipsoidal to equivalent elastic property of the composite is analyzed, and the condition of the simplificating the non-ellipsoidal particle to ellipsoidal particle was obtained. The result indicated that using the numerical method in Eshelby tensor calculation is highly precise. It is acceptable to simplify the non-ellipsoidal particle to ellipsoidal particle when the non-ellipsoidal particle is highly symmetrical. The oblate particle has more important influence on the equivalent elastic property of the composite than other shapes, and hence it cause larger error for simplifying the non-ellipsoidal to ellipsoidal particle than other shapes.