The co-combustion of coal gangue (CG) and biomass was expected to increase the utilization rate of solid waste and compensating for individual feedstock disadvantages. However, the emission of nitric oxide (NO) and ash melting characteristics during this process was of concern, but no relevant study had focused on this. In this work, the combustion behavior of Salix limb(SL)/Wheat straw(WS), CG and biomass-CG blends was studied by non-isothermal thermogravimetry and tube oven method. The results indicated that when CG was mixed into biomass fuel as an additive, the burn-out effect of CG was improved. The NO emissions from the experimental value of 80% SL/WS blend with 20% CG were reduced by 8.9%/10.1% compared to the theoretical value. Moreover, the potassium aluminum silicates with high melting temperatures were formed in the ash of the composite fuel, which reduced the serious slagging phenomenon that has been observed in the biomass combustion process. The composite fuel of 80% biomass (SL/WS) + 20% CG could promote combustion and reduce NO emissions, which was a meaningful method to treat CG to the maximum benefit and reduced the phenomenon of biomass slagging.