Abstract: Trajectory measurement system on rotary drilling, which is named YCSZ(A), has many advantages. It can provide reliable reference for drilling constructions of coal mine. The measurement results of ordinary borehole meet the practical experience and theoretical inference on the trend of rotary drilling borehole. The effect to prevent the deviation of borehole's trajectory is obvious in condition of using correction device. By the verification of the results obtained from postures measuring instrument and the trajectory measurement system, conclusions show that the blowing angles of a borehole have enormous implications for the trend of the hole. Trajectory measurement system on rotary drilling can be applied to a variety of normal trajectory measurement under different conditions, and has good compatibility and high credibility.