Abstract: 【Objectives】The effect of urea peroxide on the physiological characteristics and photosynthetic fluorescence parameters was evaluated in young peach trees exposed to waterlogging stress to provide useful information for better peach production.【Methods】Pot experiments were conducted with one-year-old peach trees, ‘Chunmei’as test materials. Firstly a pot experiment was conducted to determine the response of peach trees to waterlogging stress; then another pot trial was conducted to study the effect of urea peroxide application. Four treatments were designed: urea peroxide packed inside a bag and buried into 7 cm deep around the plants (T1); urea peroxide broadcasted into soil (T2), common urea basal applied (T3) and no N applied as control (CK). In the 0, 1, 3, 5 and 7th day of waterlogging treatment, the oxygen release characters of urea peroxide in soil, the leaf gas exchange parameters of peach trees, and the physical and biochemical index in leaf and root were determined; In the 5th day, the chlorophyll fluorescence parameters were measured.【Results】The soil surface water dissolved oxygen concentration increased after the application of urea peroxide. The water dissolved oxygen concentration always maintained at a high level under the bag control urea peroxide treatment within 7 days after treatment. The application of urea peroxide significantly reduced the decrease amplitude of net photosynthetic rate (Pn) of young peach trees leaf, stomatal conductance (Gs) and transpiration rate (Tr). Five days after treatment, the young peach trees leaf performance index (PIABS), maximal photochemical efficiency (Fv/Fm), the numbers of active reaction center per unit area (RC/Cso) were significantly higher than control, and the increase ampltitude of the heat dissipation per unit area (DIo/Cso) was significantly lower than control under waterlogging stress. The values of Chl a, Chl b and Chl (a+b) of young peach trees leaf were significantly increased by 10.72%、 10.86%、 10.87 and 5.71%、 4.78%、 5.57%, respectively, under application of urea peroxide treatments (T1 and T2) than the control. Application of urea peroxide enhanced the activities of antioxidant enzyme (superoxide dismutase, peroxidase and catalase) in young peach trees leaves and alleviated the increase ampltitude of MDA in young peach trees leaves. The root activity, root proline (Pro) content were significantly higher than control, and the root relative plasma membrane permeability and alcohol dehydrogenase activity were significantly lower than control under application of urea peroxide treatments. 【Conclusions】Our study indicates that application of urea peroxide can alleviate the influence of waterlogging stress in young peach trees by increasing the soil surface water dissolved oxygen concentration, enhancing the activities of antioxidant enzyme.