Abstract: It is of great significance to determine the safe thickness of goaf roof to ensure the safety of mine operation.In this paper, based on cusp catastrophe theory and strength reduction method, the functional relationship between roof safety factor and its thickness in Xishimen iron mine goaf is studied by using finite difference software FLAC^3D.On this basis, the influence of goaf depth, span, height, roof cohesion and tensile strength on the safe thickness of goaf roof is studied by single factor test.The results show that there are linear, nonlinear positive correlation, nonlinear negative correlation and nonlinear negative correlation between depth, span, roof cohesion, tensile strength and roof safety thickness; the influence of height on roof safety thickness is very small.The prediction model of the safe thickness of the goaf roof is established considering the four factors of the depth, span, roof cohesion and tensile strength, which provides a new research method for determining the safe thickness of the goaf roof.The prediction results of the model are consistent with the transient electromagnetic exploration results of a pyrite, which verifies the scientificity and effectiveness of the prediction model method.