Abstract: Biomass is a new type of high quality fuel with abundant reserves, wide distribution and great potential for development and utilization, and its reasonable and effective utilization has important practical significance for the goal of "carbon neutrality". A large number of scholars have carried out study on the blending of biomass on different types of coal power units, mostly using numerical simulation methods to study the impact of blending biomass on boiler combustion performance or experimental study of the blending of biomass in a single coal mill only at high load, having limited value for promotion and application. It is rare in the industry to conduct study on the key technology of blending biomass with multiple coal mills in a pulverized-coal boiler of the supercritical coal power unit. In view of the actual situation of coal power units in China operating under deep peak shaving conditions for a long time, in order to realize large-scale blending and utilization of biomass in supercritical coal power units, the characteristics of different biomass fuels were compared through proximate analysis, ultimate analysis and thermogravimetric analysis, and the type of biomass particles for blending was determined as straw particles. Then, industrial experiment study was carried out in a 600 MW supercritical lignite unit. When the boiler operated under medium and low load condition, biomass particles were blended with multiple coal mills in the whole furnace to analyze the combustion characteristics, operation safety and stability and pollutant emission characteristics of the unit under different blending ratios. Then, the output performance of a single coal mill with a blending ratio of 10% biomass particles during the low-load experiment of boiler was studied. The results show that under the deep peak shaving, the combustion performance of the supercritical lignite unit was stable when the blending ratio of the boiler was less than 10%, and there were no safety problems affecting the operation of the unit such as coking in the furnace and large accumulation of oxide in the tube, and the pollutant emissions within the standard. In the experimental process with a blending ratio of 10% biomass particles in a single coal mill, the current and pressure difference of inlet and outlet of the coal mill increased obviously, and the phenomenon of grinding blockage occured. The safety blending ratio of 7% biomass particles in a single coal mill was determined when the boiler was running at low load. The study results have made a theoretical foundation and design criteria for the large-scale application of biomass blending in supercritical coal power units under the background of deep peak shaving.