Abstract: In order to study the influence of different blending position,proportion,primary air temperature and air rate of biomass and different coal blending on NO emission and combustible matter in fly ash of boiler,the thermal experiments of biomass particle blending combustion was carried out based on a 50 kW downer pulverized coal test boiler. The results show that when the proportion of biomass input heat is 6% and biomass is mixed in from different locations,NO emissions are reduced to a certain extent,and different locations have different rates of reduction. NO emission decreases the most when biomass is fed into the reduction zone,The decrease of bituminous coal is 23.47%,and that of lean coal is 13.64%. After the biomass is mixed in,the flue gas temperature at the outlet of the furnace rises to varying degrees. The biomass blended with bituminous coal should be added in the early stage of combustion,which is more conducive to the burnout of pulverized coal,but the biomass blended with lean coal should be added in the later stage of combustion. When the proportion of biomass blended with combustion is increased from 6% to 12%,the reduction of NO emission increases from 23.31% to 39.5% when coupled with bituminous coal. When coupled with lean coal combustion,the reduction of NO emission decreases from 13.61% to about 10%. When lean coal is used as the main fuel,the absolute value of NO decrease is higher than that of bituminous coal. The reduction of NO by different biomass is related to the nitrogen content in biomass,and the lower the nitrogen content is,the greater the reduction of NO is. By increasing the primary air temperature of biomass,the content of combustible matter in fly ash decreases from 13.88% to 7.62%,and the primary air temperature of biomass should be increased as much as possible without affecting safety. The change of primary air rate of biomass has little impact on combustion efficiency.