A system for preventing inflow of exhaust gas for a vehicle, may include an inside/outside air door provided in an air conditioning device of the vehicle and controlling an amount of outside air introduced into an inside of the vehicle, an outside-air temperature sensor measuring a temperature of the outside air of the vehicle, a temperature control door disposed inside the air conditioning device of the vehicle and controlling a temperature of air discharged to the inside of the vehicle, and a control unit controlling the inside/outside air door to cause an amount of the outside air to be introduced to the inside when a vehicle speed may be equal to or larger than a predetermined speed, wherein the control unit controls the temperature control door to control the temperature of the air discharged to the inside when the temperature of the outside air deviates from a predetermined temperature range.