Abstract: The present invention discloses an improved air filter structure, comprising a container, a housing covering the container, a motor, a fan, and a stirring rod disposed at the bottom of the fan. A plant liquid or an aromatic liquid is placed in the container, and the gas outside the housing circulate continuously in and out of the container by the fan, such that the molecules of the liquid in the container can be released quickly to fill the space of a room with fragrance. A plurality of sensors is disposed at appropriate positions of the housing, and connected to a control switch. When someone is approaching the sensing range, the sensor will turn on the control switch and start the motor, so that the fan will circulate the airflow, and the stirring rod will stir the liquid to accelerate the dispersion of the liquid molecules.