Abstract: In the sample drilling task of China's lunar exploration project, the reliability of drilling machines influences its function directly, and can even lead toa success or failure of the sampling task. By analyzing the mechanical properties and high and low temperature environment of drilling tools in the whole life cycle, this paper identifies the failure mode of the drill string, summarizes the anti-loosing method of conventional thread and proposes an anti-loosing scheme of DTFLOCK thread structure, which was compared with standard thread by experiment. The new anti-loosing method provides reference for the design of connection structure of the drilling tool for the engineering departments.