A floating mechanism comprises a lift arm, a translation arm and a connection frame. One end of the lift arm is rotatably connected to the connection frame which is also rotatably connected to the translation arm. The lift arm drives the translation arm to rotate and move up and down between two intersecting planes with a fulcrum at the other end of the lift arm opposite to the translation arm. The translation arm can also be translated in a translational plane intersecting the lift arm with the connection point of the translation arm and the connecting frame as an axis. The lift arm and the translation arm of the floating mechanism can together drive an operating panel to move up and down in a vertical plane and to translate front and back, and left and right in a translation plane; meanwhile, the operating panel can be driven to rotate in the translation plane along with the lift arm and the translation arm. Also provided are an ultrasonic diagnostic apparatus with the floating mechanism and a floating support method.