Flexible pavements comprise a majority part of highways in china. Many highway bridges are constructed in these highways. These primary highway bridges are subjected to the same heavy loading as the conventional asphalt pavement, but caused much more significant damage than the conventional asphalt pavement. As hot-mix asphalt (HMA) is a visco-elastic material and the all around environment is different between road pavement and bridge deck, the structural or load-carrying capacity of road pavement and bridge deck is different. Thus, to accurately determine in situ strength characteristics of flexible pavement, it is necessary to predict the temperature distribution within the HMA layers and find the difference between road pavement and bridge deck. The majority of previously published research concentrated on pavement temperature prediction. To confirm the bridge deck temperature profile, observing the temperature at bridge deck and road pavement for two months. Compared with the temperature profile of bridge deck and road pavement, find the difference between them. Then some daily temperature prediction models are analyzed and develop a modified double-sine model to simulate the surface temperature variation of bridge deck.