The formations are extremely complicated in WFSD-4S of Wenchuan earthquake fault scientific drilling project, drilling was difficult with frequent wellbore shrinkage, collapse and block falling accidents, which brought great difficulties for the drilling construction. The sticking accident occurred at 517m depth is elaborated in detail, and the accident causes and conditions are analyzed. By means of forceful pulling, drill pipe reverse rotating, fishing by releasing spear, casing milling and some other ways, the sticking accident is smoothly processed. The treatment experience can be reference to the similar accidents.