The invention discloses a control method for an air conditioning system of an electric automobile. The air conditioning system comprises a temperature adjusting knob which is provided with a zero gear. A cold air gear and a hot air gear are arranged in the positions, on the two sides of the zero gear, of the temperature adjusting knob. A cold air side starting gear is arranged in the lower stream of the cold air gear in the direction from the zero gear to the cold air gear. A hot air side starting gear is arranged in the lower stream of the hot air gear in the direction from the zero gear to the hot air gear. In a standby state, when the temperature adjusting knob is rotated to the cold air side starting gear, a refrigeration mode is started, and when the temperature adjusting knob is rotated to the hot air side starting gear, a heating mode is started. A cold air side neutral gear is arranged between the cold air gear and the cold air side starting gear. A hot air side neutral gear is arranged between the hot air gear and the hot air side starting gear. According to the control method for the air conditioning system of the electric automobile, a passenger can conveniently and rapidly start the refrigeration mode and the heating mode through the temperature adjusting knob; and energy wasting caused by incautious operation by the passenger can be avoided by arranging the neutral gears, so that decreasing of the driving mileage is avoided.