Abstract: The gas-solid flow of a 600 MW supercritical circulating fluidized bed boiler with pant leg and six cyclones was simulated using Fluent software.The two-fluid model（TFM） approach was carried out to represent the axial and radial distribution of particles,as well as the nonuniformity of the six cyclones.Results show that the solids suspension density along the furnace height is a dense-dilute two-phase distribution.A backflow of particles was observed on the interior wall in the pant leg region.There is a double core-annulus distribution in the dilute region and a solids backflow on the furnace division wall,front wall and rear wall.Solids suspension densities on the division wall and between the wall’s gap are higher than those on the furnace walls.They also have higher values in the areas between the suspended panels compared to those out of the panels.The maximum mass flux appreas in the middle one,however there is no significant difference among the six cyclones,.