The invention provides a hydraulic cylinder. The hydraulic cylinder comprises a cylinder body, a piston is arranged in the cylinder body, a piston rod is connected to the piston, and a plurality of locking pieces are arranged on the piston rod; a plurality of columns of locking devices are arranged on the cylinder body, each column of locking devices comprise a plurality of locking mechanisms, andthe locking mechanisms can lock the piston rod by locking the locking pieces; a three-way one-way valve, a first three-way joint and a second three-way joint are arranged on the outer side of the cylinder body, an outlet of the three-way one-way valve communicates with a liquid inlet of each two-position three-way valve, and a first liquid inlet of the three-way one-way valve, an oil inlet and anoil outlet of the cylinder body at the rodless cavity end all communicate with a first outlet of a reversing valve of the hydraulic cylinder through the first three-way joint; and a second liquid inlet of the three-way one-way valve, an oil inlet and an oil outlet of the cylinder body at the rod cavity end all communicate with a second outlet of the reversing valve of the hydraulic cylinder through the second three-way joint. According to the hydraulic cylinder, the situation that positioning of the piston rod can be kept at a plurality of preset positions without depending on pressure keeping of a rodless cavity is achieved, and the use is convenient.