Co-gasification of biomass and coal offers a strategic approach to enhance the sustainability of energy resources by exploiting the inherent synergies between various biomass components (cellulose, hemicellulose, and lignin) and coal. This study investigates the co-gasification in a downdraft fixed-bed reactor, focusing on the impacts on gas yield, calorific value, and carbon structure transformations. Thermogravimetric analysis reveals that the thermal decomposition kinetics of the biomass components differ significantly, with cellulose and hemicellulose enhancing gas yield and calorific value, while lignin shows an inhibitory effect on these parameters. Cellulose improves the gasification process, particularly at a 50.00wt.% blending ratio, optimizing both the calorific value and CO production by 20.32% and 45.75%, respectively, over theoretical values. In contrast, lignin inclusion at a 70.00wt.% ratio decreases the calorific value and CO production by 6.44% and 11.21%, respectively. Additionally, hemicellulose is found to catalytically enhance CO2 conversion, with a maximum increase of 45.99% at a 70.00wt.% ratio. The study elucidates the differential impacts of each biomass component on the co-gasification process and underscores the potential of optimizing biomass blends to maximize the efficiency and sustainability of energy production.