Abstract. The TN removal efficiency is very low and the TN concentration of effluent can not meet the national standard of GB18918-2002 in the CRI system. In order to increasingly improve the denitrification efficiency of the CRI system, the artificial soil column is used to simulate the CRI system with 4 kinds of wastewater step-feeding modes. A series of comparative experiments are carried out, and the experimental results show that the TN removal efficiency of the CRI system is controlled by the denitrification process, and the denitrification process takes place mainly in the 900-1400mm zone of the artificial soil column; with the step-feeding mode, the C/N ratios of effluent from the 900-1400mm zone increase obviously in the CRI system, and in the case 4, the C/N ratios of effluent from the 900-1400mm zone are about 2, which is the closest to the optimal C/N ratio of the denitrification process; the best wastewater feeding mode of the CRI system is that the wastewater is pumped into the system from the infiltration media surface and the starting point of the anaerobic zone at the same time, with the influent amount ratio of 2:1.