A small rock core sampling drill, which is suitable for manipulator of manned submersible operation, was presented of the working principle and design requirements. The structure of the small sampling drill operated by manipulator of manned submersible was designed according to the characteristics of working conditions. The results show that the small core sampling drill is embedded with a power supply, which can eliminate the power supply and control signal from the manned submersible and greatly improve the safety operation of the manned submersible. Using magnetic trigger mode to control the start and stop of the small core sampling drill can effectively reduce the leak. The volume of the drill is reduced by using flexible shaft transmission, which makes it easy to carry the drill by the maned submersible.