The invention discloses a light full-hydraulic drilling rig for underground drilling in coal mines, which includes a frame, a drill pipe, a braid, a guide rail, a propulsion hydraulic cylinder, a hydraulic clamp and a drill power head, and the hydraulic clamp includes a clamp base , support seat, clamping hydraulic cylinder and clamper slips; water braid includes water braid housing, water braid shaft, water braid hollow shaft, two wear rings, isolation ring, front end cover, rear end cover and wear resistance Sealing ring, drilling rig power head includes reduction box body, connecting frame, gear shaft, hollow stepped shaft, hydraulic motor, spring mounting seat, spring limit seat, end face retaining ring, gear, disc spring group, power head slips and clips Tighten the hydraulic cylinder. The invention is compact in structure, easy to implement and low in cost, reduces energy consumption, improves power transmission efficiency, has stable and reliable clamping force on the drill pipe, can prolong the service life of the wear-resistant sealing ring and the braided shaft, and reduces the trouble of replacement , to ensure the construction progress and safe production, reduce the vibration of the drilling rig, and avoid the drill pipe from being broken.