The utility model discloses a cleaning device for an ash silo of a thermal power plant. Wherein the outer cover body is arranged outside the ash bin and is used for supporting and fixing the ash bin;a switch door is arranged at the front end of the outer cover body; a discharge pipe is arranged at the bottom of the ash bin; a dome valve is mounted on the discharge pipe; the top of the ash bin isconnected with a pneumatic ash conveying pipe; according to the utility model, the dust collection fan is arranged on the outer cover body to suck away ash leaked from the lower part of the ash bin and convey the ash into the ash storage tank for storage; high-pressure gas for conveying ash in the pneumatic ash conveying pipe absorbs the ash in the ash storage tank into the pneumatic ash conveyingpipe through the aslant-arranged ash discharging pipe according to the siphon principle; ash in the ash storage tank is conveyed into the ash bin, so that leaked flying ash in the ash bin is recycled, the leaked flying ash can be absorbed completely when the discharging pipe discharges materials, the atmosphere is prevented from being polluted, the surrounding environment is protected, the ash falling on the lower portion of the ash bin does not need to be treated manually, and the health of personnel is guaranteed.