In this research, the curvature of three-phase unsymmetrical composite laminates was determined based on the Rayleigh-Ritz energy method. Three-phase composite laminate consists of glass fiber, epoxy resin and multi-walled carbon nanotubes (MWCNTs). Micromechanical models including Halpin-Tsai, modified Schapery, bridging and Schapery models have been employed to determine mechanical and thermal properties of nanocomposite plates. The influence of the thickness, curing temperature and weight fraction of MWCNTs were studied analytically. Then, some cross-ply composite specimens were fabricated and the analytical results were certified by experimental ones. Additionally, the results were compared with the Hyer model. It was observed that the proposed model can predict the curvature behavior better than the Hyer model. Study of the effects of mentioned parameters on the curvature of the cross-ply laminates revealed that addition of MWCNTs leads to increase in the elastic modulus and decrease in the CTE. So, the curvature of unsymmetrical cross-ply laminates decreases by addition of appropriate amount of nanoparticles.