Abstract: In order to realize the safety and high efficiency of coal mine gas drainage, we developed a high precision measurement while drilling system based on ARM processor according to the construction environment and construction technology requirements of underground directional drilling machine, and established the mathematical model of the borehole trajectory, designed the hardware circuit of inclinometer probe, and programmed the borehole trajectory data processing software, and conducted the ground test and coal mine borehole MWD experiment. The test results show that the system with high accuracy and stability can meet the technical requirements of the measurement of coal mine underground.