A water-cooled fan includes a body having an air inlet and an air outlet; a fan unit corresponding to the air inlet or the air outlet; an installation slot placed between the air inlet and the air outlet; and a water supply unit disposed above the installation slot. A method for controlling a multifunctional fan includes configuring a functional space and providing a water supply unit at a top end of the functional space; optionally providing a honeycomb or an air filter unit in the functional space; and when the honeycomb is provided in the functional space, providing, by the water supply unit, dampening water for the honeycomb. The present invention can selectively achieve the effect of air humidification or air purification by using a honeycomb or an air filter unit as needed, and the water-cooled fan of the present invention has high intelligence. A multi-purpose set reduces the cost.