Abstract: In order to fully utilize the abundant biomass resources in the rural areas of northern China, a biomass boiler with a new furnace structure and a urea spray denitrification system were designed to solve the problem of high nitrogen oxide emission concentration in the rural biomass boilers. And biomass combustion experiments were carried out. The experiment adjusted the excess air coefficient and the proportion of primary and secondary air by changing the opening of ball valve in the air duct, and measured the NO_X emission concentration of biomass particulate fuel with the same weight under different combustion conditions. The experimental results showed that with increase in excess air coefficient α, the converted NO_X emission concentration first decreased and then increased, reaching the minimum value when α=1.1. Additionally, increasing the ratio of primary and secondary air lead to the combustion temperature in the furnace first increasing and then decreasing.Considering the combustion efficiency of the boiler comprehensively, when the air volume ratio was 6∶4, the converted NO_X emission concentration was optimal, and the converted concentration of nitrogen oxide emission was 141.74 mg/m~3. Compared with coal-fired boiler, the SO_X emission concentration of the biomass boiler was very low, and the nitrogen oxide emission of the biomass boiler with new structure was significantly reduced after adding urea solution, which showed good environmental benefits.