Abstract: After a simplified mechanics model for the internal force and deformation of the united supporting of bolt-shotcrete and steel arch has been put forward with the aid of the shell theory, the differential equations of the united supporting structure are derived, and the calculation formulas of its internal force and deformation are proposed. Moreover, the characteristics of the internal force and deformation of the united supporting structure are studied as a case. The position of dangerous section and control factor of strength design are discussed. The theory bases are provided for engineering design of the united supporting structure.