Abstract: As an essential tool for pipeline in-line inspection, caliper tool plays an irreplaceable role in dealing with hazards in pipeline. This paper firstly describes the work principle of the caliper tool, and then analyzes the possible errors caused by barycenter offset which is induced due to the vibration and gravity force in the process of testing. The actual initial angle and height are obtained for the caliper tool after it suffers from rotation and barycenter offset. Through mechanical analysis of the supporting cup, such offset in actual operation is obtained. A correction algorithm for barycenter offset is put forward to correct the offset in each instantaneous state, which effectively improves the precision of the caliper tool. This paper has a certain guiding significance for the research and development of the caliper tool technology.