The present invention relates to a combustion additive composition for preventing fouling and corrosion of biomass and waste incineration boilers using coal ash and sulfuric acid, and more particularly, tube corrosion disorders and refractory corrosion disorders caused by alkalis generated during biomass or waste combustion , In order to prevent blockage of the combustion gas passage due to the accumulation of ash on the tube surface and disturbance of heat transfer, the failure that occurs when chlorine gas (HCl) in the combustion gas is mixed with KCl and NaCl is caused by the change of the combination of sulfuric acid and the fire-resistant material. It prevents high-temperature chlorine corrosion caused by adhesion of KCl, NaCl compound, NaCl, which is generated by chlorine gas generated during combustion to the hot tube, and effective ingredients contained in coal ash change the composition of fouling to increase the melting temperature. Biomass and waste incineration using improved coal ash and sulfuric acid so that ash can be easily removed during soot blowing by changing the sticky characteristics to be smooth and smooth. Combustion to prevent fouling and corrosion of boilers It relates to an additive composition.