Abstract: To reasonably determine the load-deflection and ultimate state of two-way concrete slabs, a test for a full-scale two-way concrete slab was conducted, including the cracks and failure mode, the load-deflection, steel strain and corners' restraint forces. Based on the test results, by solving the force and moment equilibrium equations and considering the tensile membrane action, one theoretical method was established according to the yield-line theory, the proposed steel strain difference, concrete and steel strain failure criteria to predict the slabs' load-deflection and the limit loads. Meanwhile, according to the shell finite element, the nonlinear procedure was developed to predict the load-deflection, the membrane mechanics and steel strains of the concrete slabs, and the rationality of the present theoretical method was verified. The comparison of the results predicted by the present method with other methods and the test results was conducted. The result shows that:compared with the test results and other methods, the present theoretical method is simple and easy to calculate, and it is capable of predicting the ultimate state of two-way concrete slabs with reasonable accuracy.