Inlet protection device capable of being automatically closed

The utility model discloses an entrance protection device capable of being closed automatically, which comprises a safety limit door frame, the safety limit door frame is L-shaped, a multifunctional safety door is arranged on the inner side of the safety limit door frame, and an L-shaped inner groove of the safety limit door frame faces one side in a platform. The side, close to the safety limiting door frame, of the upper surface of the multifunctional safety door and the top position of the safety limiting door frame are fixedly connected with obliquely-arranged fixed connecting blocks, the L-shaped safety limiting door frame can only be opened towards one side position, falling caused by mistaken door opening of workers is avoided, the two fixed connecting blocks are arranged in parallel, and the safety limiting door frame is convenient to use. Fixed connecting holes are formed in the center positions of the end faces of the two fixed connecting blocks in a penetrating mode, and a safety reset spring is fi