The utility model discloses a pebble coal outlet and inlet self-locking system of a coal mill. The system comprises a gas source for controlling self-locking of a pebble coal outlet and a pebble coal inlet, a two-position three-way valve is arranged on a convey-out pipeline of the gas source, a first outlet and a second outlet of the two-position three-way valve are connected to a pebble coal outlet pipeline and a pebble coal inlet pipeline respectively, a plurality of one-way valves are arranged on each pipeline, and the first outlet is connected to the open end of the pebble coal outlet and the closed end of the pebble coal inlet; the second outlet is connected to the closed end of the pebble coal outlet and the open end of the pebble coal inlet. According to the work system, it can be effectively guaranteed that the pebble coal outlet and the pebble coal inlet can not be simultaneously opened or closed through gas circuit control, and the self-locking function of the pebble coal outlet and the pebble coal inlet is achieved. The problem that after a cable and a travel switch in an existing coal mill are damaged, opening and closing feedback signals are in disorder, and the pebble coal outlet and the pebble coal inlet can not be locked is thoroughly solved.