Abstract: According to the combustion characteristics of biomass materials, a new boiler structure with three air distributions was designed, and the variation characteristics of the pollution gas emission and heat loss with the change of air distribution ratio and quantity were studied. The results showed that the mass concentration of NOx changed by changing the ratio of air distributions. When the ratio of the primary air, secondary air, and tertiary air was 7:1:2, the mass concentration of NOx got the minimum value of 83.45 mg/m3. With the increase of excess air coefficient, the mass concentrations of SO2 and NOx decreased gradually; the flue dust concentration increased continuously; the total heat loss of the boiler decreased first and then increased. When excess air coefficient was 1.75, the total heat loss got the minimum value of 13.8%, and the mass concentrations of SO2, NOx and flue dust were 29.29, 83.03 and 74.90 mg/m3 respectively. This research provides the theory basis for the combustion boiler design and operation of biomass briquette with low NOx emission.