Abstract: Take the rectification of No. T-202 oil tank in Shijiazhuang Oil Refinery as an example, the paper discusses the rectification on sagged tank. No. T-202 oil tank was sagged at the location of tank shell and tank top due to the overrated negative pressure in unloading operation in January of 1999. To repair the sagged tank, an analysis on the stress of retainer ring under the internal pressure and a check-up on internal uplift and strength of retainer ring have been conducted. So, the water injection method to repair the sagged tank is selected. The rectification results have shown that this method is available and effective to repair the sagged tank.