Abstract: The phenomenon of magnetic brake in 2014 China Undergraduate Physicists＇ Tournament（ CUPT）is investigated. Through the transform between the magnetic charge and molecular current point of view,the motion and force analysis of strong magnet are carried out,from the angle of force（ mechanics） and energy. It is finally concluded that the motion state of strong magnet is related to the geometric properties of non- ferromagnetic metal tube and itself,and the physical properties of materials. The conclusion has been verified by experiments.

Key words: strong magnet, non-ferromagnetic metal tube, magnetic charge, molecular current, magnetic braking