Abstract: The factors as affecting the mechanical properties of the L80-1 oil casing are analyzed by means of making the statistics of its mechanical properties and contents of its main alloy elements and referring to its metallographic structure.It is revealed via the analysis that properly controlling the contents of the alloy elements is the key to assure the mechanical properties of the oil casing, i.e., keeping w(C)within range of 0.34%~0.36%, and w(Mn)within the range of 1.30%~1.40%.Furthermore, the temper-holding time has to be strictly controlled, and the delay time will not be longer than 30 minutes so as to assure uniform and stable mechanical properties.Finally the homogeneity of the microstructure will be also assured by means of increasing the rotation speed of the quenching lathe supporting roller up to 60 r/min.