Abstract: Described here in the article are the main aspects of the large-sized and light-wall SA106B seamless steel pipe for the nuclear island steam generator system of AP1000 nuclear power plant, including the performance characteristics, the manufacturing process and related key techniques as adopted, etc.The inspection/testing results show that all the indexes of the SA106B steel pipe has met relevant requirements under the applicable ASME specification for metallurgical quality, chemical composition, mechanical properties, and nondestructive testing, etc., being satisfactory to the need of seamless carbon steel pipes by the said the steam generator system.