The invention relates to a DCS (Distributed Control System) control method for A cooling fan of a COREX slag powder grinding system, comprising the following steps of: reading current air temperature value; comparing the current air temperature value with a preset temperature value; if the current air temperature value is smaller than the preset temperature value, shielding a cooling tower fan readying signal, canceling a cooling tower fan starting signal, shielding a cooling tower fan running feedback signal, and then starting a production line; otherwise, directly starting the production line. The invention improves the traditional DCS control method of the cooling fan, and reduces the energy source consumption and the production cost.