The invention discloses an aluminum electrolysis cell electrolyte temperature online monitoring method and device. A transmission mechanism and an infrared charge coupled device (CCD) image collection device are installed inside an upper mechanism of an electrolysis cell; an industrial personal computer issues a control instruction to an electric control device and controls the flow of compressed air flowing through a cooling device and movement of the transmission mechanism; the transmission mechanism drives the infrared CCD image collection device to vertically move and collects the temperature of an aluminum outlet of the electrolysis cell in real time according to the set sampling frequency; the infrared CCD image collection device transmits the collected image to the industrial personal computer in a wired or wireless mode; the industrial personal computer carries out processing and analysis according to a built mathematical model of the image and electrolyte temperature by the adoption of an image processing algorithm, namely online monitoring of the electrolyte temperature is achieved through monitoring of the real-time image. The aluminum electrolysis cell electrolyte temperature online monitoring method and device achieve continuous and uninterrupted monitoring and analysis of the electrolyte temperature of the electrolysis cell.