The lattice deformation tensor for martensitic transformation was found from available crystallographic data. This tensor was used for modeling of the isothermal deformation of CuAlNi shape memory alloys in the frames of a microstructural model. The simulated stress-strain curves obtained for pseudoelastic austenitic and pseudoplastic martensitic CuAlNi are in a good qualitative agreement with literature experimental data for single crystals with different orientations.