The invention discloses an air sterilizer comprising a shell. Both ends of the shell are respectively provided with an air inlet and an air outlet. An ultraviolet sterilizing lamp and a motor are mounted in the shell, and the motor is connected to a fan. The air inlet and the air outlet of the shell are respectively provided with a light barrier. The invention is characterized in that: an infrared heater is fixedly mounted on the inner wall of the shell and is in connection with a regulating switch disposed outside the shell through a lead, and the outer wall of the shell is also provided with a thermometer. The air sterilizer provided by the invention has the advantages that: it can effectively kill the bacteria in indoor air, also can regulate indoor temperature, and plays a fan role of providing cool and hot breeze, thus having very strong functionality and practical applicability.