The invention discloses a single-action hydraulic cylinder with an inner leakage display function. The single-action hydraulic cylinder comprises a cylinder body, a first screw, a second screw, an upper end cap, a piston, a piton rod, a spring, a fist piston seal, a second piston seal, a plug, an air purifier, an oil pipe, a sealing gasket, a hollow screw, a hinge connector, an oil pipe bracket, a liquid level sensor and the like. According to the single-action hydraulic cylinder with the inner leakage display function, the liquid level sensor is mounted on the side face of a nonworking cavity of the single-action hydraulic cylinder and senses the liquid level position, liquid level position data are transmitted to peripheral equipment for display and alarm, and the inner leakage condition of the single-action hydraulic cylinder is mastered in time; and if the liquid level is higher than a certain position, oil in the nonworking cavity of the hydraulic cylinder is released through the oil pipe, and oil outer leakage is prevented. The single-action hydraulic cylinder is simple in structure and reliable in work, the inner leakage condition of the single-action hydraulic cylinder can be mastered, oil outer leakage is prevented, and the single-action hydraulic cylinder has wide application prospects.