In the environment of out-field application, the temperature of the infrared remote measuring system of road surface temperature would change greatly, and the changes of the internal stray radiation thereby caused can lead to great systematic measurement error. So, infrared remote measuring system of road surface temperature based on dual window infrared detector was designed to measure the target object radiation and the internal stray radiation in real-time; meanwhile, based on the temperature effect of the detector, road surface temperature calculation model was established by eliminating the influences of internal stray radiation. The results of the calibration test show that when the working temperature of the detector and the measured target temperature are within -10-40 ℃, -10-60 ℃ respectively, the temperature effect and the radiometric calibration function can be processed linearly, showing linear superposition effect, which verifies the rationality of the road surface temperature calculation model. After calibration, out-field comparison test was conducted on infrared remote measuring system of road surface temperature and Pt100 contact temperature sensor, and it was obtained that the correlation between the measurement system and the measured data of Pt100 contact temperature sensor was up to 98.7%, among which the measurement error at night was lower than 2.78%, suggesting that the proposed system can measure the road surface temperature under out-field condition with changing environmental temperature.