The structure, principle and characteristics of a selfdesigned and manufactured experimental device for measuring metal linear expansion coefficient are introduced. On this basis, the experiment for measuring metal linear expansion coefficient is carried out. The instrument adopts portable design, the combination of physical lever and optical lever, water circulation heating, so that the metal rod to be measured is heated evenly. Three common materials, aluminum, copper and iron are measured and the experimental error was less than 3%. The design and manufacture of the instrument are mainly used for teaching demonstration, which can help students learn and understand the knowledge of linear expansion coefficient, optical lever and water circulation heating. It provides a good experimental equipment for the experiment of measuring metal linear expansion coefficient.