The system for controlling a flow of cooling air in a battery system for cooling the battery system includes: an air conditioning system which includes an outlet discharging cooling air for reducing a temperature of the plurality of battery modules, and an inlet taking in cooling air, of which a temperature is increased, after reducing the temperature of the plurality of battery modules; and a pipe which includes a plurality of module cooling ports connected to the outlet, forming a flow path of the cooling air, and corresponding to the plurality of battery modules, respectively, and makes the cooling air discharged through the outlet pass through each battery module through each module cooling port to cool the plurality of battery modules.