Based on the observations of road and bridge surface temperature and conventional meteorological data from Fenghuangguan reservoir automatic weather station along Wuying expressway from October 2009 to March 2010,the hourly variations of air temperature and bridge and road surface temperature were studied under different weather conditions including clear,overcast,foggy,rainy and snowy.The results showed that the bridge surface temperature was close to the air temperature and was usually 2 ℃ lower than the road surface temperature at night in winter.Moreover,surface freezing hours over the bridge is almost twice as long as that on the road.By using the validated underlying surface energy balance model,we calculated the energy budget elements of bridge surface at night under clear and overcast weather conditions respectively in winter,analyzed the difference in temperature changes between road and bridge surface and tried giving explanations for the phenomenon that bridge surface is apt to freeze compared with road surface.