A control method for a vehicle air-conditioning system according to one of the claims 9-12, comprising: obtaining a determination result whether an electronic expansion valve is in a fault state according to a current opening degree of the electronic expansion valve, an actual superheat degree, and a preset superheat degree acquired while performing a superheat degree control, outputting a control signal to an executive mechanism according to the determination result; and adjusting, by the executive mechanism, a parameter of a device affecting change of the actual superheat degree in the vehicle air-conditioning system, to adjust the superheat degree of the vehicle air-conditioning system; or controlling, by the executive mechanism, turning off a compressor or the air-conditioning system; wherein in determining whether the electronic expansion valve is currently in the fault state, a first time span is taken as a time determination period of the fault state to determine whether the electronic expansion valve is abnormal; and then a number of continuous abnormality times of the electronic expansion valve is accumulated; it is determined that the electronic expansion valve is in the fault state, and outputting a control signal to the executive mechanism in the case that an accumulated number of continuous abnormality times is greater than or equal to a preset number of times; and a control system outputs no control signal to the executive mechanism, and enters a next fault diagnosis cycle in the case that the accumulated number of continuous abnormality times is smaller than the preset number of times; wherein condition 1 is configured to be that the preset superheat degree minus the actual superheat degree is greater than a first fixed value and the current opening degree of the electronic expansion valve reaches a minimum value, and condition 2 is configured to be that the actual superheat degree minus the preset superheat degree is greater than a second fixed value and a current theoretical opening degree of the electronic expansion valve reaches a maximum value, obtaining a determination result that the electronic expansion valve is in an abnormal state in the fault diagnosis cycle in the case that the vehicle air-conditioning system satisfies the condition 1 or the condition 2; and resetting the accumulated number of continuous abnormality times (n) of the electronic expansion valve in the case that the vehicle air-conditioning system satisfies neither the condition 1 nor the condition 2. obtaining a determination result whether an electronic expansion valve is in a fault state according to a current opening degree of the electronic expansion valve, an actual superheat degree, and a preset superheat degree acquired while performing a superheat degree control, outputting a control signal to an executive mechanism according to the determination result; and adjusting, by the executive mechanism, a parameter of a device affecting change of the actual superheat degree in the vehicle air-conditioning system, to adjust the superheat degree of the vehicle air-conditioning system; or controlling, by the executive mechanism, turning off a compressor or the air-conditioning system; wherein in determining whether the electronic expansion valve is currently in the fault state, a first time span is taken as a time determination period of the fault state to determine whether the electronic expansion valve is abnormal; and then a number of continuous abnormality times of the electronic expansion valve is accumulated; it is determined that the electronic expansion valve is in the fault state, and outputting a control signal to the executive mechanism in the case that an accumulated number of continuous abnormality times is greater than or equal to a preset number of times; and a control system outputs no control signal to the executive mechanism, and enters a next fault diagnosis cycle in the case that the accumulated number of continuous abnormality times is smaller than the preset number of times; wherein condition 1 is configured to be that the preset superheat degree minus the actual superheat degree is greater than a first fixed value and the current opening degree of the electronic expansion valve reaches a minimum value, and condition 2 is configured to be that the actual superheat degree minus the preset superheat degree is greater than a second fixed value and a current theoretical opening degree of the electronic expansion valve reaches a maximum value, obtaining a determination result that the electronic expansion valve is in an abnormal state in the fault diagnosis cycle in the case that the vehicle air-conditioning system satisfies the condition 1 or the condition 2; and resetting the accumulated number of continuous abnormality times (n) of the electronic expansion valve in the case that the vehicle air-conditioning system satisfies neither the condition 1 nor the condition 2.