Abstract: According to the engineering features of rock-socked piles in karst region,the clamped beam model of rock-socked piles in karst region was set up at first.Secondly,based on the catastrophe theory,the cusp catastrophe model for bearing capacity of rock-socked piles and safe thickness of cave roofs in karst region were established,at the same time,the necessary instability conditions of cave roofs were deduced,and then the methods to determine safe thickness of cave roofs under piles and bearing capacity of rock-socked piles were proposed.Finally,the method was applied to two practical engineering projects and the results were satisfactory.