The invention provides a cleaning tool for a computer host. The cleaning tool comprises a roof-shaped cleaning operation bin, a host placing box, an air pressure balancing bin arranged on one side ofthe host placing box and a pressure relief bin arranged on the other side of the host placing box; the cleaning operation bin is arranged at an upper end of the host placing box, the bottom end of thecleaning operation bin is communicated with the host placing box, and a cleaning operation hole for connecting an air blower cylinder of an air blower is formed in the top end of the cleaning operation bin; and the air pressure balancing bin, the host placing box and the pressure relief bin are sequentially connected and penetrated, a balance filter for filtering contaminated air is arranged at one end, far away from the host placing box, of the air pressure bin, and a pressure relief operation hole for connecting a dust collector ventilation tube is arranged at one end, far away from the placing box, of the pressure relief bin. The invention further provides a computer host cleaning method based on the computer host cleaning tool, and the cleaning method is simple in operation, good in dust collection effect and incapable of producing secondary pollution.