The invention discloses a method and device for controlling an outdoor fan in a split air-conditioner. The method includes the steps that the current outdoor environment temperature is detected; when the current outdoor environment temperature is larger than or equal to a preset outdoor environment temperature threshold value, the gear mode of the outdoor fan is determined according to the current outdoor environment temperature; when the current outdoor environment temperature is smaller than the preset outdoor environment temperature threshold value, the current outdoor condenser outlet pipe temperature is detected, and the current operation frequency of a compressor is acquired; the gear mode of the outdoor fan is determined according to the current outdoor environment temperature, the current outdoor condenser outlet pipe temperature and the current operation frequency of the compressor. According to the method, linkage control can be conducted according to the four parameters of the outdoor environment temperature, the condenser outlet pipe temperature, the revolving speed of the outdoor fan and the operation frequency of the compressor, the air-conditioner can operate efficiently, and therefore the low temperature refrigeration capacity is improved.