Abstract: To meet the practical demand of the azimuth gamma logging tool while drilling in the geological guidance of the drilling along the seam in the ground mine, a drilling depth measuring equipment for coal mine was designed and developed, it could provide the accurate depth data of the borehole to support the azimuth gamma logging data interpretation. This paper introduces the application of depth measuring equipment in azimuth gamma logging while drilling from the aspects of composition, working principle, physical design and field test. Through the test of the exploration hole on the ground and the drilling in coal mine underground, it shows that the measurement data of the depth measuring equipment is stable, reliable and could meet requirement of the azimuth gamma logging while drilling in coal mine underground.