Abstract: To achieve ultra-low NOx emissions, biomass direct combustion power plants typically employ low excess air coefficient combustion methods to synergistically control NOx emissions. However, insufficient combustion can lead to a significant increase in the emissions of non-methane hydrocarbons (NMHC) and benzene series compounds, which are atypical pollutants that have not been extensively studied or reported. In this study, tests were conducted on NMHC and benzene series compounds in a 30 MW biomass grate furnace operating under ultra-low emission conditions. The results indicated that the emission concentrations of NMHC were as high as 3557.4-11219.7 mg/m3, and the total concentrations of six typical benzene series compounds ranged from 49.2 to 134.9 mg/m3. The most toxic compounds, benzene, toluene, and styrene, accounted for 52.6%-60.5% of the total, significantly exceeding emission standards. Increasing primary air volume and reducing boiler load were found to