Abstract: Feeding circuit is one of the main actuators of truck-mounted drilling rig, has significant influence on technical feature of drilling rig. Now a truck-mounted drilling rig is often equipped with the feeding mechanism of telescopic mast structure which is realized through the chain movement driven by two oil cylinders. It has compact structure and long feeding stroke. On the basis of analysis on load characteristics, a hydraulic control system with two-pump and two-circuit control was designed for ZMK5530TZJ100 type truck-mounted drilling rig, can meet the normal drilling demand of quick round trip and actual drilling pressure control. Through the explosion-proof relief valve mounted on the rodless chamber, the reliable hovering function was realized, will avoid the serious damage of drilling rig that is caused by free fall of drilling tool resulting from pipe cracking or misoperation. To make the two cylinders move in step, parallel connection of the synchronization control ports of two relief valves is employed to make both feeding cylinders with the same pressure. A "L" style trial borehole with the drilling length of 1 675 m in Jingcheng Sihe coalmine was successfully drilled by ZMK5530TZJ100 type truck-mounted drilling rig, validating the rationality and the reliability of the designed feeding circuit.