Abstract: A manufacturing process for Gr.B steel seamless tube used for high pressure hydrogenation unit is elaborated here in the essay involving such major aspects as chemical composition design, and manufacturing process flows of melting, rolling and heat treatment etc.Considering the corrosion characteristics of the said tube, the chemical composition design is studied, the melting process and inclusion level of the billet, and the heat treatment process for the tube are all controlled.Results of relevant tests of the tube as developed show that its metallurgical quality, chemical composition, mechanical properties, and NDT data are all in compliance with applicable requirements as specified under ASTM/ASME, and that its yield strength(≤ 345 MPa), hardness(≤ 180 HBW) and corrosion resistance are also up to the designed and operating requirements.