The scientific drilling borehole CSDP-02 in the Eastern Sea of China was completed at 2843.18m. The borehole needed to be expanded after completion to carry out subsequent research. Before expansion, the 114 mm casing needed to be pulled out; however, the casing cannot be pulled out as usual due to resistance caused by borehole failure. In this research, the hydraulic internal cutter technology was adopted to cut the stuck casing section by section, and increase the pull-out length of stuck casing per run. With this method, casing sticking was solved economically and efficiently. The detailed operation procedure and key points are presented through the field case.