Abstract: In response to the problems of piston rod extension and retraction caused by temperature changes during the use of traditional steel supported hydraulic cylinders, as well as the potential risk of support failure, a thorough analysis and research have been conducted on the locking structure of steel supported servo hydraulic cylinders. By optimizing the clearance between the piston rod and the threaded pair of the locking block, and by limiting the positional relationship between the upper and lower clamping blocks of the locking block and the locking block, the position of the piston rod is locked. Practice has proven that this scheme effectively reduces the impact of temperature changes on the displacement of the steel supported hydraulic cylinder piston rod, reduces the force between threaded pairs, achieves bidirectional locking of the piston rod in the axial direction, significantly improves the service life of the cylinder and the stability of the support structure, thereby extending the service life of the steel supported hydraulic cylinder. Its optimal method can provide reference for research on mechanical locking structures of related steel supported hydraulic cylinders.