A ventilation head cover of an engine may include a head cover main body having a blow-by exhaust portion, a baffle plate disposed in the head cover main body with a predetermined distance from the head cover main body to form a gas passage with the blow-by exhaust portion, and an oil inflow prevention wall formed to an end portion of the baffle plate and engaged with the head cover main body, wherein the oil inflow prevention wall includes at least a gas passage hole to form the gas passage.