A cleaning sachet for removing carbon deposit and rust on a gun element, and a cleaning method thereof, uses cleaning powder that includes aluminum oxide making up 75.000% to 99.989% by weight of the cleaning powder, zinc peroxide making up 0.010% to 9.000% by weight of the cleaning powder, and nano zinc oxide making up 0.001% to 6.000% by weight of the cleaning powder. A user can lay the cleaning sachet on a carbon-deposited and/or rusting area of the gun element before or after moistening the cleaning sachet with a lubricating oil, and then wipe the carbon-deposited and/or rusting area with the cleaning sachet after waiting a period of time. Therefore, the colloidal solution formed by mixing the lubricating oil and the cleaning powder and released out of the cleaning sachet can remove the carbon deposit and/or rust on the surface of the gun element.