Abstract: Affected by geological factors and engineering fac- tors,the numbers of oil-water wells on casing deforma- tion,dislocated breaking and casing leakage are increas- ing.As a result,the inner drift diameter of the casing be- comes smaller.Because the inner diameter after deforma- tion and pasting reinforcement is smaller than the external diameter,the conventional string can not meet the re- quirements of the separate zone waterflooding technology, which sharpens the injection and production in casing de- formation well field.Therefore,the string with the exter- nal diameter (?)95mm,the separate zone waterflooding technology with 15MPa withholding pressure and the cor- respondent throwing-in & pulling technology have been developed and achieved perfect effect in application.