The thermogravimetric analyzer and horizontal tube furnace are used to study the effects of operation parameters such as temperature, fuel type, and oxygen concentration on the combustion and NO emission characteristics of the rice husk, rice straw, and peanut shell in the O2/CO2 atmosphere. The results show that the combustion performances of volatile matter and fixed carbon of the three biomasses increase with the increase in the 02 content. The mean NO emission increases sharply when the reaction temperature increases from 700 to 800℃. However, it increases slightly when the temperature exceeds 800 ℃. Meanwhile, the mean NO emission and nitrogen conversion decrease with the increase in the nitrogen content in biomass. The mean NO emission changes little with different oxygen concentrations, and the NO emissions of the three biomasses are all lower than the requirement for the minimum NO emission. Increasing the oxygen concentration favors the biomass combustion in the O2/CO2 atmosphere, and oxygen concentration has little effect on the NO emission.