Based on phenomenon that both change of stress and temperature will cause elastic volumetric strains, a concept of 'equivalent stress' is introduced into a newly proposed thermoelastoplastic model. This new concept is used to formulate an equivalent subloading yield surface, an extended void ratio difference and the corresponding evolution equation in natural way, which can consider both influences of the stress and temperature. The proposed model can describe properly the general mechanical and thermal behavior of some typical geomaterials and is confirmed by laboratory tests results. For instance, increase of temperature may increase or decrease the strength of materials depending on the characteristics of the materials. Meanwhile, it is proved that the proposed model satisfies thermodynamic theorems in the framework of thermodynamics. (C) 2012 Elsevier Ltd. All rights reserved.