Abstract: For inability to directly measure attitude data of drilling tool at hole bottom and draw drilling hole trajectory during drilling process of mine-used slewing drilling rig, an off-line measurement while drilling system for mine-used slewing drilling rig was developed based on measurement while drilling principle and off-line data synchronization method. The system is composed of probe tube, synchronizer and host computer software. Probe tube measures gravitational field and geomagnetic field separately through triaxial accelerometer and triaxial magnetometer, so as to acquire drilling rod attitude. Synchronizer acquires numbers of drilling hole and drilling rod through press keys, and selects valid measuring points according to drilling rod attitude data. Host computer software draws 2D or 3D trajectory through measuring point recursion algorithm. The functional test results show that mold height of total geomagnetic field vectors measured by the system is close to real value of 50-60 μT, mold height of total gravitational field vectors is close to 1g, and the maximum dip-angle error is 1° and the maximum azimuth-angle error is 5° after correction by sensor correction algorithm. The underground test results show that trajectory of read-made drilling hole drawn by the system is basically the same as actual trajectory, but hole-mouth trajectory of drilling role is easily affected by magnetic interference of drilling rig to generate error, which leads bigger error of the whole drilling hole trajectory, so drilling rig should be 3 m away from hole-mouth at least.