Understanding scale-up effects on the hydrodynamics of a liquid-solid circulating fluidized bed (LSCFB)unit requires both experimental and theoretical analysis.We implement multigene genetic programming (MGGP) to investigate the solid holdup and distribution in three LSCFB systems with different heights.In addition to data obtained here,we also use a portion of data sets of LSCFB systems developed by Zheng (1999) and Liang et al.(1996).Model predictions are in good agreement with the experimental data in both radial and axial directions and at different normalized superficial liquid and solid velocities.The radial profiles of the solid holdup are approximately identical at a fixed average cross-sectional solid holdup for the three LSCFB systems studied.Statistical performance indicators including the mean absolute percentage error (6.19％) and correlation coefficient (0.985) are within an acceptable range.The results suggest that a MGGP modeling approach is suitable for predicting the solid holdup and distribution of a scaled-up LSCFB system.