An auxiliary cooling system which is provided separately from an engine cooling passage in a vehicle provided with a turbo engine. The auxiliary cooling system includes a first line which connects a radiator and an intercooler to each other and on which an electric water pump is installed. A second line connects the intercooler and an intake manifold. A third line connects the intake manifold and the radiator, and a bypass valve selectively directly transfers cooling water, heated while passing through a turbine housing provided on a path of the third line, to the radiator or transfers the cooling water to the radiator via an engine block or a heater. Cooling water discharged from the intake manifold passes through an ETC (electronic throttle control) unit and thus reduces a temperature of intake air passing through the ETC unit.