Abstract: Based on the service characteristics of the deep ocean-purposed seamless steel linepipe,the CB80 seamless steel marine linepipe with fine corrosion-resistance is designed and developed.Described here in the essay are the main aspects associated with the said seamless steel marine linepipe,such as the steel chemical composition analysis,the heat treatment process and mechanical properties and corrosion resistance as resulting from testing of the trail pipes.The testing results show that the CB80 seamless steel pipe is in possession of fine low-temperature toughness and resistance against seawater corrosion,good resistance against corrosion of acidic medium and physiochemical properties up to the requirements for X80Q steel as specified under API Spec 5 L—2012.After studying on the second phase particles with the extraction complex method and the transmission electron microscopy,it is revealed that the particles consist mainly the NbCand TiN precipitated phases.