An air-conditioning control method for calculating an optimum operation amount of an air-conditioning blower in an air-conditioning system of a vehicle includes: determining a heater heat quantity after an engine of the vehicle is started under a maximum heating condition of the air-conditioning system and the air-conditioning system is turned on according to current vehicle state information and air-conditioning information; determining a lost heat quantity discharged outside the vehicle during a current air-conditioning mode; determining an effective heating energy efficiency by calculating a difference between the heater heat quantity and the lost heat quantity; calculating the optimum operation amount of the air-conditioning blower where the effective heating energy is maximized; and controlling operation of the air-conditioning blower according to the determined optimum operation amount.