Biomass is a " zero carbon" renewable energy source and is of great importance to China in achieving the goal of " peak carbonemission and achieve carbon neutrality" . Although it is considered as a clean energy source, biomass combustion still emits NOx(NO,N2O) and greenhouse gases (CH4, N2O, CO2). Therefore, it is necessary to investigate the NOx and greenhouse gas emissions characteristics of direct biomass combustion. NOx and greenhouse gas emissions from a 15 MW biomass circulating fluidized bed were measured,and the effects of bed pressure, primary and secondary air ratio, front and back wall secondary air ratio, waste wood blending ratio on NOxand greenhouse gas emission characteristics were investigated. The combustion adjustment experiments show that the increase in bed pressure is beneficial to reduce NO and CO2 emissions, but the reduction is small and causes an increase in the volume fraction of CO andCH4, and a decrease in CO2 volume fraction. With an increase in the primary to secondary air ratio, NO emissions are slightly reducedwith a low CO and CH4 emission, which means that the secondary air can be reduced appropriately to reduce NO emissions. When the ratio of secondary air from front and back walls is small or large, it is beneficial to reduce NO with a low CO and CH4 emission. Whenthe mixing ratio of waste wood with high content of N is increased from 20% to 50%, NO and CO2 emissions first emissions increases andthen decreases, while the CO and CH4 show a reverse trend. This study shows that when low excess air co-efficient combustion method isemployed to control NOx emissions of the biomass circulating fluidized bed boiler, the concentration of CO and CH4 emission is significantly increased, which reduces combustion efficiency. In addition, as a greenhouse gas emission, CH4 must be considered. Combustion adjustments method is not sufficient enough to control NOx, while high amount of NH3 and HCN are emitted when some certain highnitrogen-containing fuels are burned with low oxygen combustion.