The invention provides a dust collection mechanism of a packing machine, which belongs to the technical field of machinery and aims to solve the technical problems of incapability of automatically collecting dust on cartons by an existing packing machine. The packing machine comprises a rack and a conveying platform, wherein the conveying platform is fixed to the rack. The dust collection mechanism comprises a dust collection platform and a lifting frame, wherein the dust collection platform is fixed to the rack, the lifting frame is arranged on the dust collection platform in a lifting mode,a cover plate is fixed to the lower end of the lifting frame, the cover plate is horizontally arranged and is located just above the conveying platform, a plurality of air nozzles are fixed near the edge of the cover plate, the plurality of air nozzles pass through the cover plate and are oppositely arranged, the plurality of air nozzles communicate with an air pump through air pipes, a dust collection cover is fixed to the middle of the cover plate, the dust collection cover is located below the cover plate, the upper end of the dust collection cover passes through the cover plate and communicates with an exhaust fan, and the exhaust fan communicates with an exhaust pipe. The dust collection mechanism has the advantage that the cleaning of the cartons and the collection of dust can be automatically performed.