Abstract: As the soundest workover technology, the casing replacement/retrieval technology is being paid more attentions and has become one of the major workover technologies in Daqing Oilfield. This technology involves many technologies, i.e., casing milling packer and external casing centrilizer, fish-falling proof technology for casing damaged well of small size, new/old casing mending and cementing, through-payzone casing retrieval technology, casing tool sticking prevention, etc. By applying the above technologies, the success rate of deep casing replacement/retrieval in Daqing reached up to 94%, and casing retrieval depth reached 1000 m, while the casing sticking and drill pipe milling accidents dropped to 1% or lower. The typical casing retrieval procedures are illustrated and the specific applications are also described.