A controlling method of an air conditioning system comprising at least one outdoor unit, at least one indoor unit connected with the at least one outdoor unit, a gateway configured to collect state information or operation information of the outdoor unit and the indoor unit, a data collection server to receive the state information or the operation information collected by the gateway, and a data storage server configured to store the information collected in the data collection server, the controlling method comprising: an information collecting step configured to collect the state information or the operation information of the outdoor unit or the indoor unit in a preset period by using the gateway; an information transferring step configured to selectively transfer the information collected in the information collecting step to the data collecting server in a preset period; an information storing step configured to transfer the operation information or the state information of the outdoor unit or the indoor unit out of the information transferred in the information transferring step to the data storage server and to store the transferred information in a preset period; and an information outputting step configured to output the state information or the operation information of the outdoor unit or the indoor unit transferred in the information transferring step to the output unit, characterised in that the information outputting step is configured to output the state information or the operation information to the output unit at predetermined intervals shorter than the preset period by using the data collection server, when there is information transfer requirement, wherein the transfer requirement is automatically generated at predetermined intervals, when real-time information identification is required by the user, and wherein the information outputted in the information outputting step is not stored in the data storage server in the information storing step. an information collecting step configured to collect the state information or the operation information of the outdoor unit or the indoor unit in a preset period by using the gateway; an information transferring step configured to selectively transfer the information collected in the information collecting step to the data collecting server in a preset period; an information storing step configured to transfer the operation information or the state information of the outdoor unit or the indoor unit out of the information transferred in the information transferring step to the data storage server and to store the transferred information in a preset period; and an information outputting step configured to output the state information or the operation information of the outdoor unit or the indoor unit transferred in the information transferring step to the output unit, characterised in that the information outputting step is configured to output the state information or the operation information to the output unit at predetermined intervals shorter than the preset period by using the data collection server, when there is information transfer requirement, wherein the transfer requirement is automatically generated at predetermined intervals, when real-time information identification is required by the user, and wherein the information outputted in the information outputting step is not stored in the data storage server in the information storing step.