Abstract: The root architecture, leaf reactive oxygen species and photosynthetic characteristics of potted Malus hupehensis seedlings were investigated after 10 days of waterlogging under five concentrations of hydrogen sulfide (H₂S) donor sodium hydrosulfide (NaSH,0, 0.02, 0.05, 0.1, 0.2 mmol·L^-1) and NaSH with scavenger hypotaurine (HT). The results showed that the root length, root surface-area, root volume, root diameter, root top number, fractal dimension, first lateral roots and root activity all increased, the leaf superoxide anion (O₂^-·) accumulation and hydrogen pero-xide (H₂O₂) content both decreased, the leaf P_n, T_r, g_s, WUE and CUE all raised, the plant height and biomass both increased when the 0.02-0.1 mmol·L^-1 NaHS were added to the waterlogging environment. Adding 0.1 mmol·L^-1 NaHS showed the best effects. All these parameters dropped back to the level of waterlogging alone when NaHS concentration was 0.2 mmol·L^-1 or HT was added to the 0.1 mmol·L^-1 NaHS solution. These suggested that applying an appropriate amount of H₂S could effectively alleviate the inhibition of soil waterlogging on the root growth of M. hupehensis and relieve the effects of waterlogging stress on photosynthesis and plant growth by reducing the production of reactive oxygen species and increasing CUE.