The invention discloses a combustion method for greatly improving thermal efficiency of an industrial furnace by alcohol-based clean fuel. The method comprises the following steps of: (a) designing an industrial furnace without a thermal radiation plate or removing a thermal radiation plate in a traditional industrial furnace, and arranging more than one alcohol-based fuel combustion device on the industrial furnace, wherein a burner of each alcohol-based fuel combustion device is directly aligned with a hearth of the industrial furnace; (b) taking the alcohol-based fuel as fuel of the alcohol-based fuel combustion device; and (c) feeding a prefabricated product, of which the surface cannot be polluted, into a baking chamber from a feeding hole, directly heating air in the hearth through the alcohol-based fuel combustion device, transferring the heated air into the baking chamber by a fan, and performing heat treatment, such as baking, on the prefabricated product. The combustion method has the advantages that harmful gas is not discharged, the environment is not polluted, the heat utilization ratio of the alcohol-based fuel is improved, energy conservation and emission reduction are really realized, and huge economic benefits are brought to enterprises.