Mold biomass pellets have been utilized on a 300 MW pulverized coal-fired furnace in China for the first time. Biomass was ground using the existing mill system, and without using any additional equipment. The maximum ratio of the biomass used in the experiments is 16.1% by energy input. The feasibility of grinding biomass and the safety of mill operation have been analyzed. In addition, the effects of co-firing biomass on the flame, temperature, pollutant emission, and unburned carbon in ash have been investigated. Also the characteristics of fly ash and its utilization in the concrete have been tested. The results show that existing roller mills and direct-blowing pulverizing systems can be used to grind mold biomass and to transport pulverized biomass within the limit in the flow rate of the biomass that can be processed. During the processes of biomass co-firing, the flame on the biomass injector is stable, but the outlet temperature of the furnace decreases, and the unburned carbon in the fly ash increases, when compared with the condition when firing coal only. NOx emission decreases with an increase in the biomass input. When the rate of biomass feed reaches 24 t/h in the test, the NOx emission is reduced by about 10%, but there is only a small reduction in the SO 2 emission. Investigations on the characteristics of the fly ash shows that the content of potassium and chlorine in the ash increases with an increase in the biomass feed, but co-firing biomass does not affect the quality of the fly ash to be used in the cement industry. The results presented in this paper can provide guidance for direct biomass co-firing in existing high-capacity pulverized coal-fired furnaces in China.