In order to reveal the mechanical behavior of the fiber-reinforced polymer( FRP) at elevated temperatures,8-mm glass fiber rein-forced polymer ( GFRP) rebars are investigated by the tensile tests at a range of temperatures from 10℃ to 500℃. Thus,the corresponding deterioration tendencies of the ultimate strength and the elastic modulus with the increasing temperature are obtained. Then,based on the results of both the tension tests and the TG/DSC analyses,a tensile constitutive model of three controlled parameters is proposed to describe the GFRP rebars at elevated temperatures. This model considers the material thermal properties of both the resin and the fibers and can be simplified to be a model of two controlled parameters,namely,the glass transition temperature of the resin and the soften /oxidation temperature of the fibers. After the verification,it is found that the model of two controlled parameters is in full agreement with not only the results of the elevated-temperature tensile tests from this paper but also those of FRP rebars from relative papers,and can be generally applied to the FRP rebars with different fiber types and resin mate-rials.