This paper relies on the deformation accident of the steel piles in the pile foundation of the Dawangshan mine pit project. Through theoretical analysis combined with the actual situation, The deformation treatment and mechanical analysis of the steel casing of the pier pile foundation in the karst area are carried out. The main research conclusions are as follows: (1) The deformation treatment of the pile steel casing adopts the gas cutting steel casing and the correction deformation method in the jack hole. It is supported by internal support, C30 high-flow concrete filling and grouting reinforcement; (2) The steel inner support adopts 80mm*80mm*2.5mm rectangular steel pipe, and the circumferential arrangement is divided into three triangles, and the vertical spacing is 0.5m. (3) The eight grouting small pipes and four small pipes are embedded in the piles and inserted into the caves to grout. The grouting reinforcement effect is obvious;(4) The gas cutting method is cut layer by layer. The cutting height of each layer is 50cm, the ring direction is divided into three pieces for cutting, and the two semicircles are bent by 2cm thick steel plate, and the welding is closed into a ring. The research content of this project can provide theoretical and engineering practical support for similar projects.