Abstract: This paper studies the ultimate load carrying capacity of reinforced concrete arch. The arch is subjected to uniformly nodal vertical loads. The arch fails in elastoplastic lateral deflection associated with the flezuraltorsional deformation of the arch rib. Finite displacement theory and isoparametrc concepts are applied to three-dimensional beam element with rectangular cross-section, A simulation model is set up. The formulas of three nodes beam element are developed and applied to the calculation of the ultimate load carrying capacity of reinforced concrete arch. The experiments prove that the calculation method is reasonable.