Abstract: To solve the problem that it is necessary to disassemble the clamping device when the screw drill and the coarse diameter drilling tool are lowered into the hole bottom in the directional drilling of coal mine, a top open and close style clamp with large capacity of single-piston and double-cavity is developed. In order to further study the stress of key components, the simulation and optimization analysis of the slips and bowl are carried out, and the design of key components is guided. Field test results show that the clamp has a large opening, good rough-diameter drilling tool permeability and reliable performance, and can meet the requirements of directional drilling field.