In this research, nonlinear superelastic bending of shape memory alloy (SMA) beam has been investigated. By Using the Timoshenko beam theory and applying the principle of virtual work, the governing equations are extracted. To model the behavior of SMA, the 3D constitutive model of Boyd-Lagoudas, which has been properly reduced to two dimensions, has been used. Also, with the development of a iterative nonlinear finite element model, for the purpose of obtaining characteristic of finite element beam, the Galerkin weighted-residual method has been used. In this study, by considering the different supporting conditions and force for the SMA beam, their effects on the distribution of martensite volume fraction (MVF) and stress distribution have been investigated. The results indicate that with increasing loading, the magnitude of MVF and consequently the level of hysteresis increases, which reduced the modulus of elasticity and the strength of the material and increases the deflection of SMA beam. To validate the proposed formulation, the results are compared with other experimental and numerical results that good agreement is found between outcomes.