Based on the equilibrium of combined girders, a set of models for the strain a nd stress distributions in heterostructures introduced by lattice mismatch, ther mal mismatch and the combination of the two factors are set up, and the analyti c solutions, including lattice mismatch strain, thermal mismatch strain, bending strain and the radius of curvature of the system, are also given. Furthermore, by using the models given here, strain and stress distributions in HgCdTe/CdZnTe heterostructures are calculated. The results show that both the maximum stress in HgCdTe films and the maximum stress in CdZnTe always appear at the interface between them, and that the neutral axis as a function of thickness and elastic parameters in the heterostructures are not related to lattice mismatch, lattice relaxation, thermal mismatch, and so on. In addition, the radius of curvature of HgCdTe/CdZnTe decreases with decreasing thickness of CdZnTe. In order to avoid cracking of HgCdTe/CdZnTe device at 77K, the thickness of CdZnTe must b e larger than the limited value.