The invention relates to a water-gas separation sewage treatment purification filter. The bottom of the outer cavity of a purification tank is provided with an aeration pump through a supporting platform; a cylinder body with a filtering material is arranged in the outer cavity of the purification tank; an outer baffle ring is arranged outside the upper opening of the cylinder body and the upper opening of the cylinder body is in hanging connection with the inner wall baffle of the outer cavity of the purification tank through the outer baffle ring; a filter material screen type gland is arranged on the upper opening of the cylinder body, and a filtering gap is formed by the filter material in the cylinder body; a water-gas separation cover is arranged outside the filter material screen type gland; the water-gas separation cover is provided with gas vent holes; meanwhile, a drainage groove is arranged on the water-gas separation cover; the drainage groove corresponds to a water outlet;and the bottom of the outer cavity of the purification tank and the bottom of the cylinder body form an aeration purifying water tank. According to the invention, the filtered purified water flows out from the upper part in a reverse filtration mode, and the filtered impurities are precipitated at the bottom of the outer cavity of the purification tank, so that the cleaning and pouring are convenient. Meanwhile, the marsh gas and poisonous gas are discharged from the gas vent holes of the W-shape cover, so that the sewage treatment purification reaches the emission standard.