Abstract: A tensile experiment was conducted at different temperatures for glass fiberreinforced polymer(GFRP) bars using glass fibers with diameters of 16 mm and 22 mm. The effects of environmental temperature, fiber diameter and constant temperature time on tensile properties of GFRP bars were investigated. The results indicated that the GFRP bars did not show a significant change in apparent failure characteristics under the lowtemperature environment, and their ultimate tensile strength increased with a decrease of temperature in the range of -20~0 ℃. Furthermore, the modulus of GFRP bars containing fibers with a diameter of 16 mm was reduced with a decrease of temperature, whereas that with a diameter of 22 mm maintained a stable value. However, these two types of GFRP bars presented little change in the temperature of 0~20 ℃. The mechanical properties of GFRP bars tended to be stable after being kept in a low temperature for 1 h. The constant temperature time almost showed no effect on the bars.