Abstract: Elaborated here in the article is the development process of the large-sized and heavy-walled S890 high strength/toughness seamless steel tube for hydraulic cylinder service. The finished tube’s properties are tested,and its microstructure is analyzed. As a result,it is concluded that the said tube as developed with the“EF steel-melting+LF+VD+pilger mill rolling+quenching and tempering”process has all of its performance indexes up to the customer design requirements,including good low-temperature impact toughness and excellent weldability,being worth massive production.