Abstract: Due to engineering and formation problems in oil and gas wells in South China Sea, serious casing damage is common in old wells. In order to effectively solve the problem of casing damage in oil and gas wells, a complete set of casing retracting technology was developed for the treatment of casing damage wells, and the domestic design and development of casing retracting device and supporting tools were realized. Among them, the tie-back adopted the external tie-back mode, which can minimize the influence on the existing production casing diameter, realize the rapid recovery of casing damage well, effectively improve the production cycle of single well, and increase the economic benefit of single well. In the practical application of a well in the western oilfield of South China Sea, the wash-over fishing and end face grinding operations were carried out for the casing of the old well, and then the casing string with the casing connector was successfully connected to the bottom hole casing, and the pressure test was qualified, which effectively verified the casing connector technology and provided a good reference for the repair of similar casing damaged wells.