This paper presents the thermal stress characteristics of polystyrene plate - thin plaster wall. Based on thermal stress analysis module of ANSYS software, a three-dimensional element solid5 is selected to mesh the wall model, which can simulate the coupling effects of thermal stress and structural stress field. The critical temperature of hot and cold cycles is taken as the critical temperature condition, which is imposed on the calculation model. Windowless Wall and window wall were modeled separately. Temperature field, thermal stress, and deformation distribution were proposed after comparing and analyzing the two simulation results. Numerical simulation results indicate that: (1) Whether in high or low temperatures, window or windowless, polystyrene plates thin plaster wall insulation system has very good thermal insulation properties；(2) Polystyrene plate - thin plaster wall insulation system is influenced by the temperature stress. Different stress fields concentrate significantly around windows and in the middle of wall especially around the windows. In fact, it is relatively same as the law of cracks around the windows.