The invention provides a contactless automatic frequency tuning filter with a leakage prevention chamber, which includes a first cavity having a first housing and a first opening in the first housing,a movable member and a second cavity, and the second cavity has a second housing, a first chamber in the second housing, and a second opening and a third opening through the second housing, the movable member is inserted into the first cavity from the third opening or between the third opening and the first cavity from the third opening, The second opening is adjacent to the movable member and forms part of the chamber, and the second housing has spaced portions adjacent to the movable member to separate the movable member from the chamber, and the first housing and the second housing are notin contact with the movable member. The invention can solve the problems of leaking electromagnetic wave and instability of frequency displacement when the center frequency and bandwidth are adjusted.