Abstract: The product yields and gas composition were examined for fast co-pyrolysis of bituminous coal with either hemicelluloses-rich corncob or lignin-rich pine sawdust. The results indicate that the interactions among pyrolysis products cause an obvious difference in the yields and gas composition during the co-pyrolysis processes. As compared with pyrolysis of individual fuels, the co-pyrolysis of corncob can generate more CO₂ and H₂O due to its high content of hemicelluloses. K in biomass is easy to evaporate and transfers to the surface of coal char. The catalytic effect of K can promote the gasification reactions of coal char with CO₂ and H₂O to produce activated H and hydrogen-rich components, which can couple with radicals to inhibit polycondensation reactions between macro radicals. As a result, the co-pyrolysis increases the gas and liquid yields and decreases the char yield. For co-pyrolysis of bituminous coal and pine sawdust, Ca in pine sawdust can transfer to the surface of coal char to promote the cracking reactions of tar liquids and generate more CO₂, CO and hydrogen-rich radicals. The co-pyrolysis reduces the char and liquid yields and raises gas yield. The gasification and cracking reactions of pyrolysis products (char, liquids and gases) produce more secondary hydrogen-rich components to raise hydrocarbons and CO content in the gaseous products.