Abstract: Based on the lower-hybrid-drift instability theory in the magnetopause,a diffusive magnetosphere model is presented.Since there will be an anomalous resistivity in the magnetopause determined by the HLD instability,the magnetic field of the magnetosphere will diffuse outward and the plasma in the magnetosheath will diffuse inward.The outward diffused magnetic field determines the thickness of the magnetopause and the inward diffused plasma forms the plasma mantle.The inward diffused plasma also brings a small part of momentum and energy of the solar wind into the magnetosphere and drives the convection of the magnetosphere.