Abstract: Research on the vibration characteristics of the drill rod system in a coal mine drilling robot is essential for the prediction and control of drilling trajectories. Considering the complex interaction mechanisms between the drill rod system and coal seams during horizontal drilling, an experimental platform and vibration monitoring system for the coal mine drilling robot were established. Horizontal drilling experiments were conducted under various layering conditions of soft and hard coal seams and different seam inclination angles. The empirical mode decomposition method was used to decompose, filter, and reconstruct the collected data to eliminate noise interference and study the vibration characteristics of the drill rod system under interlaced soft and hard inclined coal seams. The results showed that as the inclination angle of the coal seam increased, the longitudinal, transverse, and torsional vibration amplitudes of the drill rod system increased when the robot was drilling through hard→medium-hard→soft or soft→medium-hard→hard coal seams. At the same inclination angle, the vibration amplitudes in the longitudinal, transverse, and torsional directions were higher when drilling through soft→medium-hard→hard coal seams than through hard→medium-hard→soft seams. When the inclination angle was small, the interlaced soft and hard coal seams had a greater impact on the drill rod system's vibration characteristics, whereas at larger angles, the seam inclination angle had a more significant effect than the layering. Moreover, larger sand and gravel particles had a certain impact on the vibration of the drill rod system.