This paper presents the result of using a softened truss model with different softened constitutive laws of concrete to predict the torsion strength of reinforced concrete beams. And, that solution will reveals to experimental data. The results of predictions show that the softened constitute laws of concrete proposed by Zhang and Hsu (1998), Belarbi and Hsu (1991), Vecchio and Collins [Model A] (1998), and Ueda et al. (1991) can well predict torsion strength of reinforced concrete beams.