Abstract: Complex situations occurred in well Q1 during well abandonment. Lots of difficulties affected casing retrieving work. The cement sheath of Φ244.5 mm casing returned to wellhead, and couldn't be pulled out after it was cut off. At last, the engineers adopted extreme way to pull the casing out by moving the cut depth up repeatedly. Due to the shallow cutting depth of Φ244.5 mm casing, Φ508 mm^*Φ339.7 mm casing couldn't be pulled out in regular way unless designing the special cutting BHA and retrieving method, This pas-sage introduced the retrieving BHA and method in detail, it also gave a reference to subsea wellhead retrieving unconventionally.