Abstract: Based on the failure mechanism of vierendeel truss, four secondary moment functions are developed according to plastic stress distribution at the perforated section of composite beam in ultimate limit state. A method for ultimate strength analysis of steel and concrete composite beams with reinforced rectangular web openings is presented, which can account for the contribution of the concrete slab to the shear strength of the composite beam. The calculated results show that the bending and vertical shear capacity of composite beam with web opening can be effectively enhanced by reinforced opening. The vertical shear capacity increases notably with the increase of stiffener plate area, and concrete slab has significant contribution to the shear strength. Comparison shows that the theoretical results agree well with the experimental and finite element method (FEM) results, with some examples illustrating the accuracy and reliability of the present method.