A method for controlling switching between operating modes of an indoor unit in a multi-split air conditioning system, wherein, the multi-split air conditioning system comprises: an outdoor unit, a shunt device and a plurality of indoor units (21, 22, 23, 24), the outdoor unit comprises: a compressor and a four-way valve, the shunt device comprises: a first heat exchange component, a second heat exchange component, a first throttling component arranged between an outlet of a first heat exchange flow path of the first heat exchange component and an inlet of a first heat exchange flow path of the second heat exchange component, a second throttling component arranged between an outlet of a first heat exchange flow path of the second heat exchange component and an inlet of a second heat exchange flow path of the second heat exchange component, a bypass valve (SVME) arranged between the outlet of the first heat exchange flow path of the second heat exchange component and a low pressure pipeline of the shunt device, and a heating control valve (SV1B, SV2B, SV3B, SV4B) and a refrigeration control valve (SV1, SV2, SV3, SV4) corresponding to each indoor unit (21, 22, 23, 24) in the plurality of indoor units, the first throttling component comprises a first control valve (SVMC), the method comprises: when any indoor unit in the plurality of indoor units receives a mode switching instruction, sending, by the indoor unit, the mode switching instruction to the shunt device; performing, by the shunt device switching control on the heating control valve (SV1B, SV2B, SV3B, SV4B) or the refrigeration control valve (SV1, SV2, SV3, SV4) corresponding to the indoor unit (21, 22, 23, 24) according to the received mode switching instruction, releasing a pressure by controlling the second throttling component, the first control valve (SVMC) and the bypass valve (SVME) to reduce a differential pressure across the refrigeration control valve (SV1, SV2, SV3, SV4) or the heating control valve (SV1B, SV2B, SV3B, SV4B) corresponding to the indoor unit, obtaining a switching flag bit of the four-way valve, and controlling the refrigeration control valve or the heating control valve corresponding to the indoor unit and the four-way valve according to the switching flag bit of the four-way valve. when any indoor unit in the plurality of indoor units receives a mode switching instruction, sending, by the indoor unit, the mode switching instruction to the shunt device; performing, by the shunt device switching control on the heating control valve (SV1B, SV2B, SV3B, SV4B) or the refrigeration control valve (SV1, SV2, SV3, SV4) corresponding to the indoor unit (21, 22, 23, 24) according to the received mode switching instruction, releasing a pressure by controlling the second throttling component, the first control valve (SVMC) and the bypass valve (SVME) to reduce a differential pressure across the refrigeration control valve (SV1, SV2, SV3, SV4) or the heating control valve (SV1B, SV2B, SV3B, SV4B) corresponding to the indoor unit, obtaining a switching flag bit of the four-way valve, and controlling the refrigeration control valve or the heating control valve corresponding to the indoor unit and the four-way valve according to the switching flag bit of the four-way valve.