The invention provides prefabricated building blocks, a wall body built by the building blocks and a building method of the wall body, and belongs to the field of building blocks. The problem that existing building blocks have low intensity and poor thermal insulation effect is solved. The prefabricated building blocks includes bodies, the insides of the bodies are provided with a steel structure skeleton, the outsides of the bodies are provided with concrete blocks, the steel structure skeleton includes a main frame plate and two auxiliary frame plates, the two sides of the main frame plate is perpendicularly connected with one sides of the auxiliary frame plates, the prefabricated building blocks further include two connection plates parallel to the main frame plate, one sides of the two connection plates are arranged in an opposite mode, the other sides of the two connection plates are perpendicularly connected with the other sides of the two auxiliary frame plates, each concrete block includes a lateral plate fixed on the external lateral faces of the main frame plate in a fitting mode and a wall plate fixed on the external lateral faces of the two auxiliary frame plates in a fitting mode, each concrete block further includes two insulation plates, the three sides of one insulation plate is perpendicularly connected with the main frame plate, one auxiliary frame plate and one connection plate, and the inner lateral sides of the two insulation plates are provided with semi-circular gap grooves. The self-intensity of the prefabricated building blocks is high, at the same time, the intensity of the wall body built by the prefabricated building blocks is higher, and the thermal insulation effect is better.