Abstract: An air-conditioning system for a vehicle may include a cooling unit including a radiator, a cooling fan to introduce air in the radiator, a water pump connected to the radiator through the cooling line, and a reserver tank provided on the cooling line to store a cooling fluid, a first condenser connected to the cooling line between the radiator and the reserver tank such that a cooling fluid is introduced and a refrigerant is introduced through a refrigerant line, and the refrigerant is condensed by heat exchange between the cooling fluid and the refrigerant, and a second condenser serially connected to the first condenser on the refrigerant line such that a condensed liquid phase refrigerant is introduced, and disposed on a front of the radiator such that the refrigerant is condensed by an air cooling type through heat exchange between the refrigerant and an outdoor air introduced on driving.