Abstract: Elaborated in the essay are the characteristics, manufacturing process and quality of the hi-strength/hi-toughness CS-Q890 seamless steel tube for crane boom fabrication. The tube is of well-mated high strength and high toughness and excellent weldability owing to optimization of the chemical composition, and adaption of the manufacturing process of converter/EAF melting→LF refining→VD refining→CC round→rolling with the Φ159 mm 3-roll retained mandrel mill/the Φ180 mm Accu-Roll mill→quenching-and-tempering treatment. The successful development of this type of product has brought about the possibility for being free of the long-time dependence on import of similar products for home-made large cranes.