3D temperature field and thermal resistance of new energy-saving wall blocks are calculated with finite difference method in order to save land resources and reduce the engineering cost of the main structure of buildings, and the equivalent thermal conductivity coefficient is connected with the thickness of air layer in the calculation to make the calculation results more accurately reflect the thermal performance of wall blocks. Many factors affecting the thermal resistance of blocks such as heat transfer coefficient, delay time are analyzed in this paper, and many methods for the improvement of thermal resistance of wall blocks are put forward. It is shown in the research that new composite walls have good effects on the winter and the summer, and its thermal stability and indoor comfort are increased significantly compared with traditional non energy-saving walls.