The method to check the air distribution is usually that a certain thickness (550-650 mm) materials with physical properties similar with the bed material for boiler operation are laid on the air distribution plate. Start the induced draft fan and the primary air fan, slowly increase the air volume, and observe the moving of bed materials. When the bed materials are approximately fluidized bed, pay attention to watching the bed surface, judge whether there is fluidization dead angle by means of dipping method. Under condition of bed material fluidization, suddenly stop air supply, observe the situation of material layer, if the materials surface is smooth, it is shown that the air distribution is basically even, and the material fluidization is good; If the materials surface is not smooth, the place with thick material layer shows that the air volume is small, the low-laying place shows that the air volume is larger. If this situation is found, it is possible to check whether the air hood is blocked or whether there is air leakage locally. Generally only when the air distribution is seriously uneven, can the uneven phenomenon of materials surface be seen.