Abstract: The technological requirements for the steel tube for fabrication of the hydraulic cylinder casing are presented. And the causes for the poor effectiveness of the previously-employed quenching & tempering treatment process for the said tube are analyzed. Based on the analysis result,a new quenching & tempering process is put forward. Following the new process,the tube is first heat treated to be fully pre-stress relieved,and have stable structure so as to prevent any deformation,when it is undergoing the quenching & tempering treatment. Then the tube is subjected to the quenching & tempering treatment to get the material’s comprehensive mechanical properties properly adjusted. As a result,the tube is generally in possession of such advantages as high strength(hardness),good wear-resistance,high plasticity,high pressure-resistance,low decarbonization rate,and slight deformation,etc. Owing to the said new heat treatment process,the tubes as made are in compliance with the technological requirements for the hydraulic cylinder casing.