The invention discloses a variable refrigerant flow system and a low-temperature control method thereof. The method comprises the following steps of obtaining the current operating mode of the variable refrigerant flow system; if the current operating mode of the variable refrigerant flow system is a pure refrigeration mode, obtaining the current outdoor environment temperature and judging whetherthe current outdoor environment temperature is smaller than or equal to the first preset temperature or not; and if the current outdoor environment temperature is smaller than or equal to the first preset temperature, obtaining the evaporation temperature of at least one indoor unit of multiple indoor units and the preset target evaporation temperature and controlling the opening degree of a throttling assembly according to the evaporation temperature of at least one indoor unit of multiple indoor units and the preset target evaporation temperature. By means of the low-temperature control method, during low-temperature refrigeration, the low pressure of a refrigeration indoor unit is prevented from being too low by controlling the opening degree of the throttling assembly arranged on a low-pressure air pipe of a throttling device, so that the refrigeration indoor unit is effectively prevented from freezing, the refrigeration indoor unit can conduct refrigeration continuously, and therefrigeration effect is ensured.