The invention relates to an ash silo dust exhaust device of a thermal power plant. The ash silo dust exhaust device of the thermal power plant comprises a stirrer and a deduster, wherein the stirrer is positioned on a transfer layer at the upper layer; an outlet of the stirrer is provided with a blanking sleeve which can convey dust stirring objects into a transport vehicle at a transfer layer at the lower layer; a dust exhaust pipeline which is communicated with an inner cavity of the blanking sleeve and an inlet of the deduster is arranged between the blanking sleeve and the deduster; the dust exhaust pipeline is also provided with an auxiliary sucker; a suction opening of the auxiliary sucker is positioned in the transfer layers; the dust exhaust pipeline comprises branch pipelines and a master pipeline; inner cavities of the blanking sleeves of a plurality of ash silo dust exhaust devices are respectively communicated with the branch pipelines; the plurality of branch pipelines are respectively connected to the master pipeline; the master pipeline is connected to the inlet of the deduster; the blanking sleeve is a telescopic sleeve; the ash silo dust exhaust device comprises a driving device capable of driving the blanking sleeve to stretch up and down. The device can effectively collect dust in an ash silo, and reduce pollution.