Thermal exchange between liquid and solid is a common problem for various engineering structures. The thermal stresses caused by temperature change have great influence on the engineering structures. A three dimensional model for a coupling thermal and mechanical field was established to investigate thermal stress under heat loading. In this study, the three dimensional Green's functions for fluid and isotropic thermoelastic two-phase materials with internal heat source are obtained and used to study the thermal stress problems between solid and liquid. By virtue of the compact three-dimensional general solutions expressed in harmonic functions, four newly introduced harmonic functions are constructed, and all components of coupled field are expressed in terms of elementary functions which are very convenient to use. Numerical results are given graphically by contours. The corresponding analysis will contribute to obtain stress characteristics of the fluid-solid thermal coupling field.