Abstract: Both pumice and nano hydrous iron oxide (NHFO) are commonly used adsorbents in water treatment. In this study, NHFO was loaded onto pumice by co-precipitation method to explore its adsorption performance and mechanism of ammonia nitrogen. The effects of initial ammonia concentration, initial pH value and co-existing ions (H⁺, Na⁺, K⁺, Mg²⁺) on NHFO@pumice adsorption of ammonia nitrogen were investigated. SEM-EDS and XRD were used to characterize the morphology and structure of NHFO@honeycomb. The results show that the initial concentration of ammonia nitrogen is 20 mg/L and the pH value is around 7. The co-existing ions have an inhibitory effect on the adsorption of ammonia nitrogen, and the inhibitory strength is H⁺>Na⁺>K⁺>Mg²⁺. SEM-EDS, XRD, FTIR and other characterization methods confirmed that NHFO was successfully loaded on the honeycomb, and the adsorption process was consistent with Langmuir adsorption isotherm (R²=0.9886) and quasi second-order kinetic model (R²=0.9969). The mechanism of ammonia nitrogen adsorption mainly includes electrostatic interaction of hydroxyl group and NH₄⁺, ion exchange and pore adsorption. This study provides a theoretical basis for the treatment of ammonia-nitrogen water by adsorption.