The fuel tanker manhole cover is installed on the top of the tank, with built-in breathing and emergency exhaust functions, and can be installed on the manhole cover oil recovery valve, oil quantity hole, anti-overflow detector rod, etc., anti-overflow sensing system in the process of filling oil, when the liquid level reaches the detection position, the sensing system will automatically alarm, so as to stop filling oil. The built-in breathing valve keeps the internal pressure of the oil tank stable in the process of oil transportation, and reaches the balance with the external pressure. The design of the pouring to prevent overflow makes the tank car keep sealed in the case of an accident. The emergency exhaust device will automatically open and release the pressure in the tank when the pressure in the tank rises sharply, thus preventing accidents and greatly improving the safety of oil transportation.