Abstract: The paper analyses the structure and the principle of the common mortar bolt,and simplifies the bearing plate which supported by the wall-rock stress to the mechanical model of the simple annular plate which supported uniformly distributed loading.Based on the deflectional differential equation of the annular thin plate on the state of axisymmetric bending,the deflection equation is gained,and then the constant of A ₀、B ₀、C ₀、D ₀ according as the boundary condition.The paper discusses the engineering application through three examples,therefore it provides a more simple,convenience and exact new method for the state monitoring of wall-rock.