The utility model discloses an air -breather for oil tank degasification, including setting up at the weight valve at oil tank body top, setting up in the oil tank body outside and with the filter equipment of weight valve intercommunication and be used for being connected weight valve and filter equipment's breather pipe, open at oil tank body top has the installation through -hole that is used for installing the weight valve, it is interior through installation component and oil tank body sealing connection that the installation through -hole is put into to the weight valve. The utility model discloses simple structure, the transformation is with low costs, the security performance is high, when the oil tank breather can't be arranged or lead to inner diameter of air hose and can't satisfy, has played and has avoided the fuel filling to jump the rifle and prevent that the fuel consumption oil tank from inhaling flat effect, has improved the ventilatory effect of fuel tank.