Abstract：The stress and displacement solutions of contraction of spherical cavity under drainage are obtained by neglecting the influence of the elastic deformation in plastic zone. The effects of corresponding parameters are discussed. The relationship between the support pressure and the radius of the elasto plastic boundary is revealed. It is shown that the smaller the radius of cavity is，the smaller the plastic region is for the same depth and the arching effect is more obvious. The deeper the borehole is，the smaller the plastic region is for the same radius. When support pressure is decreased，the plastic region is increased. The maximum displacement occurs at the cavity wall. The dilation angle has an obvious effect on the cavity displacement and little effect nearby the boundary. With the increment of dilation angle，the cavity displacement is increased.
