Drilling along a specified route is required in more and more applications. This paper introduces a path controllable drilling device based on fluid power, which requires no electric power and thus especially suitable for mine rescue. The mechanism design, control method and working mode of the most important part of the device, a 3-DOF hydraulic steering system, are illustrated. An analytical model is also provided to estimate the invisible posture and orientation of the steering system and thus the drilling path of the device as working underground.