Abstract: Thermal stress in two layer concrete slab is composed of threee parts: (a) inner stress due to nonlinear distribution of temperature in slab section, (b) warping stress due to reaction restraint of foundation, and (c) stress due to restraint strain of interface. An expression is derived for calculating the thermal stress due to restraint strain of interface with different bonding condition, and the characteristic of restraint strain of interface is also analysed and formulated with conventional temperature regime in concrete pavements.