The invention relates to a quick changing device for a functional unit of a road sweeper. The quick changing device includes a lifting device, a lifting push rod, an inclined pull rod, an oil cylinderrear cover part of the lifting device is fixedly connected to a mounting frame matched with the machine body, a cylinder rod part of the lifting device is fixedly connected to an installation frame matched with a lifting push rod, and the part, covering the interior of the machine body, of the lifting push rod is connected to the installation frame matched with the machine body, and the quick changing device is characterized in that the other end of the lifting push rod is connected with a quick changing device, one end of the inclined pull rod is connected with the quick changing device, andthe other end is connected with the lifting push rod; the quick changing device comprises an automatic push rod, an automatic push rod locking block, an automatic push rod locking block sliding railand a self-locking device. The self-locking device comprises a connecting plate, a connecting plate locking block, a functional unit connecting plate, an upper locking opening and a lower locking opening. The connecting plate and the connecting plate locking block are fixed to the quick changing device after being connected in a welded mode, an opening is cut in the functional unit connecting plate to form the upper locking opening, and a groove is formed in the lower end of the functional unit connecting plate to form the lower locking opening.