The invention relates to an air-conditioning system which comprises an indoor machine and an outdoor machine, wherein the outdoor machine comprises a condenser, a condensation fan, a temperature sensor, a pressure sensor and a control panel, wherein the temperature sensor is used for collecting temperature; the pressure sensor is used for collecting condensation pressure; the control panel is used for detecting whether the pressure sensor and/or the temperature sensor malfunction/malfunctions, regulating the rotation speed of the condensation fan according to the condensation pressure collected by the pressure sensor when the pressure sensor does not malfunction, regulating the rotation speed of the condensation fan according to the temperature collected by the temperature sensor when the pressure sensor malfunctions but the temperature sensor does not malfunction, and controlling the rotation speed of the condensation fan according to default parameter values when both the pressure sensor and the temperature sensor malfunction. Through implementing the technical scheme provided by the invention, the control method can be automatically switched when a single control method is invalid, and the normal and efficient operation of the air-conditioning system can be ensured.