The Theoretical calculation and the finite element method (FEM) are used for studying the thermal property of hollow-block and hollow-masonry. The method of appendix in the standard for Thermal Design of Civil Buildings is adopted to calculate the thermal resistance and the average thermal conductivity of hollow-block and hollow-masonry. ANSYS is used for simulating temperature distribution and heat flux law under connective loads. The conduction and convection phenomena are taking into account in this study for four different values of the mortar conductivity and four different values for the bricks. The thermal resistance and the average thermal conductivity of hollow-block and hollow-masonry is the key factor for reference.