The invention discloses a gravity hydraulic booster. The gravity hydraulic booster is characterized in that an L-shaped cylinder body (9) is arranged, and the wall thickness of the L-shaped cylinder body (9) is 20cm. A base (6) is arranged for plane stability at the bottom of the L-shaped cylinder body (9) through a stable support (16), in the L-shaped cylinder body (9) hydraulic oil (7) is injected into the L-shaped cylinder body (9) to 5.5 meters and four weight supports are arranged; a counter weight (18) is arranged at the upper portion in the L-shaped cylinder body (9) in a matched mode, a rubber mat (8) is arranged at the lower end of the counter weight (18), two discharge ports (3) are symmetrically arranged between the heavy punch (18) and the hydraulic oil (7); the counter weight is connected with an operation box (5) through a stay wire (4), a motor (1) and a brake valve (2), an attached cylinder vacuum zone (17) is formed at the tail end of the L-shaped cylinder body (9), and is connected with a rack push rod (12), a rack which is positioned on the upper plane of the rack push rod (12)meshes with a gear (13), the other end of the rack push rod (12) is provided with an air rubber mat (14), a motor A (10) and an attached cylinder section (15) are arranged on the upper plane of the rack push rod (12), and the opening of the attached cylinder section (15) is provided with a brake valve A (11). The gravity hydraulic booster has the advantages of stability, safety, timing, speed safety and the capability of automatically running in the required stroke or position, and is suitable for matching application of drying equipment.