The present invention discloses a multifunctional compressed air foam fire-extinguishing device which comprises a fire-extinguishing spray gun, an air compressor and a high-pressure water pump, wherein: the fire-extinguishing spray gun comprises a mixing chamber, a foaming chamber and a nozzle which are connected in sequence; the mixing chamber is communicated with the foaming chamber and the high-pressure water pump, and a check valve disposed on the mixing chamber wall is communicated with the air compressor via a valve piping; a cylindrical cavity filter screen is arranged inside the foaming chamber; and the air compressor is also connected a adjustable foam adding valve piping in parallel. According to the present invention, the fire-extinguishing spray gun is integratedly and compactly designed, and matches with a pneumatic foam proportioning mixing device, and the high-pressure water pump is connected with the fire-extinguishing spray gun; so without any decompression, injection pressure of extinguishing media is high; and through a proportional pressure regulating valve, a throttle and the check valve of the mixing chamber, the proportions of each medium can be adjusted. The fire-extinguishing device of the present invention is easy to move, and is suitable for a variety of fire extinguishing media; and meets the requirements of different fire scenes.