The invention discloses a desktop computer case anti-dust device. The device comprises an upper mesh hole plate, lower mesh hole plate and a connecting rod; filtering holes are formed in the upper mesh hole plate and the lower mesh hole plate, the four corners of the lower surface of the upper mesh hole plate are provided with hook-and-loop fasteners, and the surface of the upper portion of the lower mesh hole plate is provided with hook-and-loop fasteners; the overall connecting rod is of a rectangular cubic structure, and hook-and-loop connecting sticks are arranged at both upper and lower ends of the connecting rod. The desktop computer case anti-dust device is simple in structure and low in manufacturing cost, sponge blocks used for dust collection and filtering are convenient to assemble and replace, on the condition that a computer case power supply fan is not influenced to absorb air, 80% or above of dust is effectively prevented from being absorbed into the case, the dust can be well prevented from entering the case and being adsorbed on computer hardware, accordingly the service life of the computer hardware is effectively prolonged, the asset waste is reduced, and the device has the advantages of being capable of improving the use performance of a computer and maintaining the interior of the computer case clean for a long time.