The present disclosure relates to a system for controlling an air flow rate into a vehicle engine room. The system includes: an air intake port receiving an exterior air at a front portion of the vehicle and supplying the air into the engine room; air ducts formed at both sides of the air intake port and introduce the exterior air into a wheel side in order to improve aerodynamic characteristic; a control valve configured to selectively convey the air flowed in the air intake port into the air ducts; a radiator disposed between the air intake port and the engine room; and a control portion configured to control the control valve based on an operating state of vehicle. The air ducts are selectively communicated with the air intake port and disposed at upstream of the radiator.