A multi-split system and a control method thereof are provided. The control method comprises the steps of: obtaining a discharge superheating degree from a compressor (3) and determining whether the discharge superheating degree is less than a first predetermined superheating degree; if the discharge superheating degree is less than the first predetermined superheating degree, further obtaining a pre-valve supercooling degree of a cooling throttle member (21), and determining whether the pre-valve supercooling degree is less than a predetermined supercooling degree; and if the pre-valve supercooling degree is less than the predetermined supercooling degree, controlling the degree of opening of the cooling throttle member (21) to remain unchanged, adjusting a vent target superheating degree of a plurality of indoor units (300) to a first target superheating degree, and controlling an indoor throttle member (21) of the plurality of the indoor units (300) according to the first target superheating degree. The method controls the cooling throttle member (21) to remain unchanged when the pre-valve supercooling degree of the cooling throttle member (21) is low, and controls the indoor cooling units (300) according to the adjusted target superheating degree, thereby rapidly setting the pre-valve supercooling degree of the cooling throttle member (21) while ensuring stable operation of the compressor (3).