In the process of deep peak regulation of supercritical circulating fluidized bed units,in addition to the problems of stable fluidization of air distribution plate and nitrogen oxide control under low load conditions faced by subcritical units,the safety of hydrodynamics is also involved. In view of the technical problems of deep peak regulation of supercritical circulating fluidized bed boiler,through the reconstruction of flow pattern,the critical fluidization air velocity was reduced,the air volume needed to ensure stable fluidization was reduced,and the combustion share in the lower part of the furnace was reduced. Furthermore,the area of air distribution plate was reduced to ensure the stability of ultra-low load fluidization,and the working fluid flow of secondary rising water wall with vertical tube ring was developed to ensure the hydrodynamic safety of low load. Reduce the particle size of bed material and circulating material,on the premise of ensuring fluidization and combustion,reduce the proportion of primary air,strengthen the local reducing atmosphere on the surface of coke particles,optimize the arrangement of coal feeding,slag discharge and air supply,ensure the uniformity of oxygen and temperature distribution in the furnace,provide a guarantee for the control of nitrogen oxides,and finally realize the stable operation of 350 MW supercritical circulating fluidized bed boiler under 20% BMCR conditions. The maximum wall temperature deviation is 17 ℃,and the temperature deviation of the same layer in the furnace is less than 30 ℃. In addition,in the process of boiler operation from start-up to full load and variable load,the temperature deviation of the inlet flue gas temperature of the three cyclone separators is always within 10 ℃,and the NOx emission is ultra-low at full load.