The invention relates to the field of environmentally-friendly devices for fly ash stabilization treatment in a waste incineration plant, and concretely relates to a fly ash solidification system stirrer dedusting and dehumidifying device. The fly ash solidification system stirrer dedusting and dehumidifying device comprises a stirrer, a fly ash weighing bucket, a solution weighing bucket, a Venturi negative pressure tube and a blower; the fly ash weighing bucket is arranged above the stirrer, and is connected with the fly ash inlet of the stirrer through a valve and a pipeline; the solution weighing bucket is arranged above the stirrer, and is connected with the solution inlet of the stirrer through a valve and a pipeline; a dry ash outlet, with a perforated top, at one side of the stirrer is communicated with a negative pressure pipeline, and is communicated with the fly ash weighing bucket through the blower and the Venturi negative pressure pipeline to form a closed loop; and a humid gas outlet, with a perforated top, at the other side of the stirrer is communicated with the solution weighing bucket through a negative pressure pipeline to form a closed loop. The device avoids the leakage of fly ash to the surrounding environment, caused by a positive pressure formed in the stirrer, in order to achieve the purposes of purifying the operating environment and reducing the particle inhalation risk of the operating personnel.