A new structure of injection zone with double-layer nozzles has been proposed in order to improve the product distribution of FCC process. Two supplementary nozzles are added below the primary nozzles. However, the research on gas?solid flow characteristics in this novel injection zone is rarely reported. In this study, the numerical investigation of the mixing and flow of catalyst/particles and oil/gas in the novel injection zone was carried out using the combination of two-fluid model with the energy minimization multi-scale (EMMS)-based drag model. The particle?wall specularity coefficient was first determined by comparing with experimental data. Four combination types of double-layers nozzles with a distance of 0.5 m between primary and supplementary nozzles were investigated, i.e. down?down, down?up, up?down and up?up types with different feeding directions. The hydrodynamic behaviors of gas and solid in the feedstock injection zone with these four nozzle combinations were investigated and further compared with the results with the single-layer nozzles. The results showed that the introduction of the supplementary nozzles had a great influence on the gas?solid flow in the feedstock injection zone, especially in the injection region with the primary upward feeding nozzles. The jet from supplementary nozzles can accelerate gas and solid phase to reach the uniform and stable state at the region above the primary nozzles. But an uneven distribution of solids volume fraction occurred at the zone above secondary nozzles. When the main nozzles were downward, the injection zone with single-layer nozzles showed the smaller mean residence time and heterogeneity. When the main nozzles were upward, the double-layers nozzles with the up?up structure showed the smallest mean residence time and heterogeneity. These results indicated that the feeding using double-layer nozzles can achieve the strong mixing within a shorter contact time and inhibit the over-cracking of desired products, thus increasing the yield of desired products.