Abstract: Combustion is the most common technology of converting biomass fuels to energy. It has the advantages of low cost, low risking, and high efficiency, and can be regarded as proven technology. In this article, various issues and topics concerning biomass combustion and co-firing are discussed. First, physical and chemical characteristics of biomass fuels are introduced. Next, combustion and co-firing technologies are discussed. The main combustion technologies are grate furnace, underfeed stokers, fluidized bed combustion and dust combustion. The coal/biomass co-utilization can be categorized by direct co-firing and gasification. Then, problems of low melting point of ash such as agglomeration, fouling and slagging are discussed. Finally, environmental pollution of biomass combustion is analyzed and an overview of the current R & D needs concerning biomass combustion is provided.