In the structural design of composite pavement with concrete pavement slab overlaid with asphalt surface course, it is very important to estimate temperature gradient in the concrete slab. The asphalt surface course reduces the temperature gradientin the concrete slab, resulting in the reduction of thermal stress of the concrete slab. In this study, this effect was investigated by the temperature measurement in model pavements and themal conductivity analysis. Based on the investigation, the relationship between the reduction effect and the asphalt thickness was derived for the structural design.