The invention discloses a ventilation fan with a humidifying function for winter. The ventilation fan comprises a ventilation fan body, a control circuit, a humidifying device, a ventilation switch and a humidifying switch; the temperature is measured through a temperature sensor, the temperature value is sent to the control circuit, the control circuit carries out contrastive analysis on the temperature value and outputs a command, if the temperature surpasses the set upper limit value, the ventilation switch can be triggered automatically to exchange air for the inside; the humidity is measured through a humidity sensor, the humidity value is sent to the control circuit, the control circuit carries out contrastive analysis on the humidity value and outputs a command, if the humidity is lower than the set lower limit value, the humidifying switch can be triggered automatically to humidify the inside so as to control the indoor temperature and humidity in a range which makes people feel comfortable. In general, the ventilation is performed before humidifying. The water level in a water tank is monitored through a liquid level sensor, if the water level in the water tank is lower than the lowest water line, a main power of the ventilation fan is cut off automatically to protect the equipment.