The oxy-fuel co-combustion behavior of two herbaceous biomass species (Bermuda grass and cornstalk) with bituminous coal was investigated by thermal gravimetric analysis (40 degrees C/min). The incorporation of Bermuda grass or cornstalk could improve combustion indices of the bituminous coal. Once blending the biomass with bituminous coal, ignition temperatures of blends could be advanced by about 100-170 degrees C. With increasing the oxygen concentration or blending ratio, the comprehensive performance index of the most blends and their parent samples increased. For the 80%grass/20%coal blend, there was a strong synergistic effect in its parent samples at 60% oxygen concentration.