Abstract: This paper investigated the water wall of a 350 MW supercritical circulating fluidized bed boiler,made some reasonable simplification and divided it into calculation circuits. By considering boiler headers as pressure nodes and according to the equations of mass,momentum and energy conservation in circuits and nodes,a hydrodynamics calcula- tion mathematical model for supercritical circulating fluidized bed boiler was built. Based on the model,the hydrody- namics of the boiler was calculated and analyzed. The result shows that the flow rates in the middle part of left wall and right wall are lower than those of front wall and back wall. The boiler can still work safely and reliably under BMCR, 75% THA,50% THA and 30% BMCR heat loads,the highest wall temperature in vertical direction is not higher than 450 ℃ ,the highest wall temperature difference at same height in neighbor circuits is lower than 50 ℃ with 10% hori- zontal heat load difference.