The distribution characteristics of FCC catalyst particle concentration in two catalytic cracking pre-lifting structure (with and without central tube) were investigated using optical fiber. The radial nonuniform index was also introduced to quantify the heterogeneity of particle concentration. The results show that the gradient of particle concentration of the structure with central tube in the expanding area (central tube area). While in the riser entrance area, the distribution of particle concentration in the structure with central tube is more uniform. Compared with traditional structure, radial Non-uniformity index of particle concentration in the two structures of riser sharply decreases 65% with central tube and 75% without that. The empirical model of the axial distribution of average solid holdup in the structure with central tube was put forward. The calculated values are in good agreement with the experimental ones, it can be used for engineering design purpose.