Abstract: Briefed in the paper are the development background, the manufacturing process flow and the main technical specifications of the super 13Cr oil tubing.The main causes for the typical defects of the said tubing as occurred during piercing and hot-rolling processes are investigated via related physical inspection and chemical analysis as well as metallographic analysis.Accordingly, relevant improvement measures are proposed and taken. Also elaborated here are the physical quality level and the feedback from the field operation of the super 13Cr oil tubing as produced with the improved manufacturing process.The analysis identifies that the existance of ferrite δ is the main cause for the said defect.Therefore ferrite δ will be effectively controlled via actions as proper design of the chemical composition of the 13Cr steel, and strict control of the billet heating temperature.