Abstract: Based on the investigation and analysis to the corrosive perforation period of casing with different wall thickness completed in 1970’s in the same block of Maling field of Longdong unit, Changqing Oilfield, this paper presents the conception of "basic wall thickness" used in the corrosive perforation of casing, theoretically analyzes and predicts the service life of thick casing, evaluates 3 methods for delaying the corrosion in the casing, and points out that the input output ratio is the highest if the wall of the casing is thickened in the Londong unit of Changqing Oilfield. The method of thickening the casing wall has been applied in some adjustment wells and renewed wells in Longdong unit. This is the test firstly conducted at home for extending the service life of the casing by thickening its wall.