Abstract: in this paper, the axisymmetrical ultimate punching Strength of concrete slabs is obtained by using the twin shear strength theory. Rigid-plastic model has been adopted, an axisymmetrical failure mechanism given, the envelope of failure Mohr circles is found to be two straight lines. Then,the upper-bound of ultimate punching load is obtained by the virtual work equation. The numerical results are shown to be satisfactory compared with known results.