Abstract: Introduced in the article is the manufacturing process of N80 class 1 steel grade oil casing concerning the following aspects:optimizing the material composition design basing on Mn-V medium carbon steel;adopting an EF smelting+refining+VD+continuous casting process for CC round billet;controlling the RHF heating temperature to be 1 250-1 280℃;controlling the billet descaling water pressure to be 13-20 MPa;realizing "high temperature big deformation" rolling at the austenitic recrystallization area as well as the non-recrystallization area by adopting a controlled rolling process.The testing results show that the N80 class 1 steel grade oil casing made by the controlled rolling process is in compliance with the requirements of API Spec 5CT-2011 for N80 class 1 steel grade in terms of yield strength, tensile strength, elongation after fracture and impact energy.