Modeling, design, and operating of circulating fluidized bed (CFB) reactors require quantitative studies on the flow structure and hydrodynamic heterogeneity, which has a significant influence on the process reactions. This study comprehensively investigates the axial and lateral distributions of the solidss concentration with superficial gas velocity of 5-9 m/s and a solidss circulation rate of 100-300 kg/(m(2)s) in a pilot CFB reactor of 14 m height. Empirical models are developed based on the above experimental data for both axial and lateral solidss concentrations. The predicted values by the proposed correlations are in good agreement with the experimental data within deviation of 10-20%. An empirical correlation to calculate the radial nonuniformity index (RNI) is proposed to quantify the nonuniformity of the gas-solidss flow. Using the RNI empirical correlation, the flow development can be also calculated quantitatively, showing a good agreement with the results obtained from the data of solidss concentration directly.