Abstract: A serials dual-strings were complicated in structure and the wellhead facilities and down hole tools have been neglected for years in Bohai offshore oilfield, which made the following well-repairing very difficulty. In order to solve this problem, these daul-strings were dug out and replaced by single-strings with simple structure and reliable and practical in use after technological improving. Based on the successful practice of Bohai center oilfield 34-2/4, well-repair matching technology for changing the daul-strings into single-strings was introduced in this paper, which provided experiences for same wells-repairing in follows.