Abstract: In the conventional cased hole completion operations, sump packer is used to support the upper part of sand control string, reduce the axial stress, and separate the well completion string from artificial bottom of well. There is a risk in the course of the operation, because the sump packer is irrecoverable. The traditional approach is to set milling fish once the sump packer was set down advancing in the well completion operations. After the incident of sump packer’s premature setting occurred at Jinzhou 9-3F2-7 well in Bohai Bay,through accurate positioning,hydraulic cutting knife is used to cut and damage the supporting slips,and then the sump packer is fished with trip spear. The successful experience of the well, provide a more convenient and simple way to save time, greatly improving the operating efficiency, for the future handling of similar incidents.