The invention discloses a self-cleaning breather valve which comprises an upper casing, a lower casing, a float, connection portions, a gasket, grids and spray pipes. The upper casing is connected with the lower casing through bolts of the connection portions. The float is located in the upper casing. The gasket and the grids are arranged between the upper casing and the lower casing. One ends of the spray pipes are connected with spray portions, and the other ends of the spray pipes are arranged at the top end of the upper casing. The self-cleaning breather valve is additionally provided with a spray pipe system which washes sludge in a vent pipes and in the upper casing; spiral sheets capable of effectively cleaning blocked sludge on the upper casing are additionally arranged on the float; meanwhile the grids are improved so that the mud entering amount is increased.