The present invention provides an air conditioning system for an electric vehicle and a method for controlling the same in which heat generated from a drive motor during vehicle running is used to assist the heating of a vehicle interior so as to provide more efficient heating of the vehicle interior and, especially, reduce the amount of battery power consumed for the heating of the vehicle interior, thus increasing driving distance and improving fuel efficiency. The air conditioning system of the invention can cool the drive motor, heat the vehicle interior using waste heat of the drive motor, and purify the air supplied to the vehicle interior with the use of a single blower.For this purpose, the present invention provides an air conditioning system for an electric vehicle, the air conditioning system including: a blower for blowing air; a drive motor configured to receive the air blown by the blower; an air purification system for purifying the air blown by the blower and supply the purified air to a vehicle interior; a second valve for supplying the air blown by the blower to the drive motor and the air purification system, respectively; and a third valve for supplying the air passing through the drive motor to the outside of the vehicle or to the air purification system, wherein the air passing in turn through the drive motor and the air purification system is supplied to the vehicle interior, thus heating the vehicle interior.