The effects of different diffusion models are studied for electron distribution of plasma sheath about reentry bodies. The diffusion velocity of electron due to density gradients is much larger than that of ions because the weight of the electrons is about three orders in magnitude less than that of the ions. Both the charge separation and its induced electric field exert an influence on the particle diffusion. The electron density distribution is obtained with numerical solution under these conditions. The results are compared with other diffusion models such as the quasi-neutral model，ambipolar diffusion model，etc. It shows that the quasi-neutral assumption is valid in most region of the flowfield，but the charge separation occurs near the body surface. The dimension of the thin layer with charge separation is in the same order of Debye shield length. The electric particle distribution is influenced somewhat by the boundary effects although the neutral moleculars and atoms are unaffected. The applicability of these diffusion models is judged through their comparaision of the numerical solution.