The invention discloses a self-thermal-insulation mortar including, by weight, 20-40 parts of cement, 5-60 parts of yellow sand and 1-8 parts of a main activator, wherein the main activator is hydrotalcite or a hydrotalcite-like material. In the formula of the self-thermal-insulation mortar, the cement, the yellow sand and the main activator are compounded so that a synergetic effect is achieved. A complex reaction between microscale polyvalent metal ions in the cement and the main activator is carried out, and then the microscale polyvalent metal ions is complexed at a quartz sand-water interface or a silicon dioxide-water interface for activating surfaces of the cement and the quartz sand to change a conventional stacking status of the cement, thereby forming a giant network complexing structure in the system. Meanwhile, when the main activator is complexed with the microscale polyvalent metal ions, interlayers in the main activator is expanded to uniformly form nanopores of which diameters are about 1-5 nm, so that the building block is excellent in strength, thermal-insulating performance, water-retaining property, constructability and the like.