The invention discloses a dissolved air floatation sewage processing device with a self-cleaning function, and belongs to the technical field of industrial sewage processing devices. The provided sewage processing device comprises an underframe, a coagulation reaction area, a dissolved air pump, a gas / liquid separating tank, a contact reaction area, a scum separating area, a slag scraping device, and a clean water area, wherein the dissolved air pump, gas / liquid separating tank, contact reaction area, scum separating area, slag scraping device, and clean water area are arranged on the under frame and communicated with each other through corresponding parts. The sewage processing device is characterized in that the gas / liquid separating tank is connected to the scum separating area through a cleaning electromagnet valve and a cleaning releaser, the cleaning releaser is composed of releasing pipes, which are evenly arranged in the scum separating area, each releasing pipe is provided with a small hole, the cleaning releaser is connected to the gas / liquid separating tank through the cleaning electromagnet valve, and a perforated water collecting pipe is arranged above the cleaning releaser, and is connected to the clean water area through a clean water electromagnet valve. The provided dissolved air flotation sewage processing device can automatically remove settled scum left in an air flotation device by controlling the related electromagnetic valves and cleaning release through an automatic control technology so as to guarantee the water quality of discharged water, moreover, the structure is simple, thus the device is easy to promote, and a reliable sewage treatment method is provided for the small and micro enterprises.