Abstract: The punching failure of concrete slabs is simplified as a problem of plane strain. The combined stresses on the shear-compression zone of concrete slabs at the momemnt of punching failure are analyzed by the twin-shear stress three-parameter strength criterion, and the ultimate vertical shear stress on the shear-compression plane is obtained. By means of equilibrium conditions, a formula of ultimate punching shear strength of concrete slabs is derived. The calculated results are in good agreement with the experimental results of 246 specimens in domestic and foreign literature. The analytic method is clear in physical conception, and the theoretical expressions can be used as reference in structural design.