The disclosure includes: judging whether a center line of an object to be scanned is deviated from a rotation axis of a gantry of a CT scanning device； determining a first distance by which the center line of the object to be scanned is deviated from the rotation axis in a case that the center line of the object to be scanned is deviated from the rotation axis； determining according to the first distance a second distance by which the shape filter is to be translated in each projection angle； and controlling the shape filter to make it translate by the second distance in each corresponding projection angle.
