The invention provides a mechanism for controlling materials to fall one by one. A cavity in a sleeve is through vertically and used as a material falling channel, and the material falling channel canonly allow one material to pass and allow two materials to be vertically stacked in the channel. A swing arm mechanism is arranged on one side wall of the sleeve. The swing arm mechanism comprises aswing arm arranged in the material falling direction, a supporting rod assembly supporting the swing arm on the side wall of the sleeve and an extending and retracting mechanism driving the swing armto swing in a reciprocating manner on the vertical face. The swing arm can be driven by the extending and retracting mechanism. The swing arm can be driven by the extending and retracting mechanism toswing in the reciprocating manner on the vertical face perpendicular to all hinged shafts, so that a bearing plate can be supported at the bottom of the lower material in the material falling channeland a suction cup deviates to the position outside the side wall of the sleeve or the bearing plate deviates to the position outside the side wall of the sleeve and the suction cup passes through a vertical long hole to suck the upper material in the material falling channel. The mechanism can achieve sequential one-by-one falling of the materials.