Abstract: During tripping slip type whipstock in sidetracking process, whipstock set sticking occurs sometimes, leading to being unable to sidetrack designed positions. Because the whipstock is special in structure, shape, and material, once being stuck, it is very difficult to handle, with low success ratio. The accident reasons are analyzed from the aspects of field operation, tool quality, and wellbore quality, and the technical difficulty for treating the accident is pointed out. It is summarized that according to different setting situation, some treatment could be selected from, such as casing changing, window cutting position elevating, etc., which are applied in real cases with good effect, supplying reference to similar accident treatment.