Demolishing of frame building by blast is complex and difficult. Based on mechanics process of demolishing blast of frame building, the numerical compute model on breaking of the frame building is set up in the paper. By this numerical compute way, the design projects of demolishing blasting of the frame can be simulated and the design parameters can be optimized. Through the simulation, the wastes of boreholes, explosive charges and safety protection material can be avoided. Sometimes the frame building does not collapse in the process of the demolishing blasting because the design project is not correct by experience. The situation of every member of the frame in the demolishing blasting can be computed by the present simulation way and the collapsing of the frame after blasting can be ascerlained. The numerical model offers a new design way for demolishing blast of frame building.