The invention discloses an air flotation separation device, comprising an external cylinder (2), a rotational flow mixed cylinder (8), a first slag-retaining cylinder (7), a first scum drainage pipe (4) and a scum collecting guide plate (10); wherein, the bottom end of the first slag-retaining cylinder (7) and the bottom of the external cylinder (2) have spacing so as to form a water passage; thebottom of the side wall of the rotational flow mixed cylinder (8) is connected with a water inlet pipe (16) which enters in tangent direction; the periphery of the top of the external cylinder (2) isprovided with a clean water collecting trench (14); and the scum collecting guide plate (10) is a strip-typed plate in an involute shape, with the involute direction right opposite to the water rotational flow direction in the rotational flow mixed area (A). Compared with the prior art, the air flotation separation device does not need to add external energy cleaning systems, achieves the object of long-term continuously and stably running, and ensures that the requirement that the micro air bubbles adhere to the dispersed oil, emulsified oil and dissolved oil of small particle size as much as possible is met, thus achieving the object of high-efficiency separation of oil from water. The air flotation separation device is especially suitable for low-consistency water containing oil.