Abstract: Described in the article is the systematic research and development of the large-sized(Φ339.7mm) hi-strength oil casing. Both the initial trial manufacturing and the optimized trial manufacturing of the said tube are performed, based on which, the chemical composition of the material, the rolling process, the heat treatment process and the tube finishing processes, etc are finalized. The results of both the pilot and massive productions have shown that the properties of the tubes are up to the quality level of foreign-made similar tubes, being highly appropriated by customers.