The scattering efficiency factors or internal electric fields of the representative ellipsoid，cylinder， cube and other five kinds of particle shapes are investigated by discrete dipole approximation and electrostatic approximation methods，and the depolarization factors under external electric field in different directions are calculated. Furthermore，a simple method to obtain the depolarization factor of a dielectric particle in different shape is given. The results can help students understand the relationship between the shape of medium and the intensity of depolarization field，and it also provides some references for the study of depolarization factor.