Abstract: Elaborated here in the article are quality characteristics, the manufacturing process and critical techniques of the large-sized, heavy-wall P280GH seamless steel tube for the main feed water flow control system of the nuclear island of Hualong No.1 Nuclear Power Unit.And the product performance of the said tube is tested.The result shows that the P280GH seamless steel tube has been in compliance with relevant requirements as specified under applicable technical specification in terms of metallurgical quality, chemical composition, mechanical property and NDT etc., and also has met the requirements for the carbon steel seamless tube as used by the main feed water flow control system of the nuclear island of Hualong No.1 Nuclear Power Unit.