Due to high temperature when drying products for this high temperature industrial oven, energy saving is rather important to users. Therefore, we developed energy saving heat exchanger which can utilize the exhaust gas to preheat the fresh air in the oven. By this means, energy savings and stable temperature can be achieved. Otherwise, we can take full advantage of the heat produced by other parts, for example, the heat from insulating layer, for recycling. As a result, the cost is reduced greatly.