A fast fluidized bed riser with 16m height and 0.10m ID was operated with FCC particles and in a wide range of operating conditions.The superficial gas velocity Ug ranged from 3.5m8226;s-1 to 8.1m8226;s-1

and the solids circulating rate Gs was from 50kg8226;m-28226;s-1 to 201kg8226;m-28226;s-1.Time series signals of solids holdup fluctuation were measured at a frequency of 900Hz using an optical fiber located at 8 axial and 11 radial positions.The nonlinear method was used to analyze the time series and consequently Kolmogorov entropy was calculated to describe the dynamic characteristics of the gas-solid flow behavior in the annular-core section. The results showed that Kolmogorov entropy could describe the annular-core flow structure. According to three marked characteristics of Kolmogorov entropy in the radial direction

three flow regions were identified：random-particles-controlled core region

chaotic-particles-controlled transitional region

wall-controlled annulus region.The change of Kolmogorov entropy in the radial direction was also interpreted based on the influence of solids on gas turbulence structures.