Downhole trouble often occurs while drilling in karst formation, which is very difficult to deal with and lead to great economic loss. Grouting reinforcement was operated in limestone formation of cave fracture and experimental study was made on bored cast-in-place pile technology. The result shows grouting reinforcement can solve the low efficiency of hole forming, downhole trouble and slurry concrete seepage in limestone formation, and it can be the reference to bored pile construction in karst formation.