A control method of an air conditioner system which comprises one or more groups each comprising an outdoor unit and a plurality of indoor units, the method comprising: when a preset reception rate degradation error occurs in one or more indoor units among a plurality of indoor units belonging to a particular group, transmitting a channel switch request signal to an outdoor unit belonging to the particular group; transmitting, by the outdoor unit belonging to the particular group, a channel scan start command to the plurality of indoor units belonging to the particular group; performing a channel scan by each of the outdoor unit and the plurality of indoor units; transmitting, by the plurality of indoor units, channel scan results to the outdoor unit; determining, by the outdoor unit, a channel for use of the particular group based on a result of a channel scan performed by the outdoor unit and the channel scan results received from the plurality of indoor units; and outputting, by the outdoor unit, information on the determined channel to the plurality of indoor units; wherein the determining of a channel for use comprises, when there is a plurality of channels having a load occupancy rate of 0%, determining that a channel with a greatest difference in a load occupancy rate from an adjacent channel among the plurality of channels having the load occupancy rate of 0% is the channel for use, wherein when a No Reception event, which indicates that no signal has been received for a predetermined period of time, occurs in one of the plurality of indoor units belonging to the particular group, checking, by an indoor unit where the No Reception event has occurred, a signal corresponding to the particular group, when a signal corresponding to the particular group is found in a second channel other than a first channel which is currently in use, switching a communication channel to the second channel, when a signal corresponding to the particular group is not found, transmitting the channel switch request signal to the outdoor unit belonging to the particular group. when a preset reception rate degradation error occurs in one or more indoor units among a plurality of indoor units belonging to a particular group, transmitting a channel switch request signal to an outdoor unit belonging to the particular group; transmitting, by the outdoor unit belonging to the particular group, a channel scan start command to the plurality of indoor units belonging to the particular group; performing a channel scan by each of the outdoor unit and the plurality of indoor units; transmitting, by the plurality of indoor units, channel scan results to the outdoor unit; determining, by the outdoor unit, a channel for use of the particular group based on a result of a channel scan performed by the outdoor unit and the channel scan results received from the plurality of indoor units; and outputting, by the outdoor unit, information on the determined channel to the plurality of indoor units; wherein the determining of a channel for use comprises, when there is a plurality of channels having a load occupancy rate of 0%, determining that a channel with a greatest difference in a load occupancy rate from an adjacent channel among the plurality of channels having the load occupancy rate of 0% is the channel for use, wherein when a No Reception event, which indicates that no signal has been received for a predetermined period of time, occurs in one of the plurality of indoor units belonging to the particular group, checking, by an indoor unit where the No Reception event has occurred, a signal corresponding to the particular group, when a signal corresponding to the particular group is found in a second channel other than a first channel which is currently in use, switching a communication channel to the second channel, when a signal corresponding to the particular group is not found, transmitting the channel switch request signal to the outdoor unit belonging to the particular group.