Abstract: For producing extra large-sized medium light-walled seamless steel tube，the medium frequency（MF）hotexpanded steel tube process is indispensable. Described here in the article are such aspects of said process as the origination and early-stage development，the evolution and certification of the product standard as well as the recently emerged new technologies and innovation achievements. Also detailed are the application situations of the MF hot-expanded seamless steel tube in the fields like thermal power generation，nuclear power generation，heat-supply piping network. petrochemical industry and large-capacity gas cylinder production，etc. It is pointed out that both quality and safety of the MF hot-expanded seamless steel tube is completely satisfactory to relevant high-end application fields. Furthermore applicable suggestions concerning selection of such tube are proposed for related design-engaged companies and users.