Abstract: According to the requirements of China Mining Products Safety Approval and Certification Center, the explosion-proof level of the part used for borehole trajectory measurement instruments within the borehole should be upgraded from the original "ib" level for coal mines to "ia" level. The borehole trajectory measuring instrument requires high precision and intelligent control to ensure accurate positioning of the borehole trajectory and to eliminate gas blank zones.The paper introduces a borehole trajectory measurement system, providing the three major components of the system and their functional characteristics. The design takes into account both countable and non-countable fault categories, adopts a three-level overcurrent and overvoltage protection principle, and performs circuit design and parameter calculations for the probe. The design of the probe's inclination and azimuth data acquisition,storage, communication circuit, and data preprocessing technology is developed, along with parameter configuration and borehole trajectory processing acquisition software. Data is transmitted to a mobile APP for analysis and mapping. In addition, the intelligent self-diagnosis judgment rules of the instrument have been studied, allowing the instrument to automatically diagnose the performance status of key components and provide prompts, thereby improving the reliability and safety of the instrument’s use. After laboratory measurement accuracy testing and underground coal mine field verification, the developed borehole trajectory measuring instrument not only meets the “ia” level explosion-proof requirements but also has wide applicability to boreholes, high accuracy in test data, and a convenient operation mode. The instrument’s self-diagnosis function is practical and effective. The research results provide new technical means for precise gas drainage in coal mines, which helps with gas outburst control and ensures the safety of workers.