Through a pot soil-culture experiment in greenhouse, the effects of exogenous H₂O₂ treatment with different concentrations (0, 0.02, 0.04, 0.06, 0.08, 0.1, 0.3 mmol/L) on the growth, photosynthetic system, and fluorescence characteristics of Z. jujube seedlings under the stress of 0.05 mmol/L Cd were studied. The results showed that:(1) Under Cd stress, the growth of Z. jujube seedlings was inhibited. After H₂O₂ treatment, the Cd resistance coefficient, photosynthetic chlorophyll content, net photosynthetic rate (P_n), transpiration rate (T_r), and stomatal conductance (G_s) of Z. jujube seedlings increased, while H₂O₂, malondialdehyde (MDA) content, and intercellular CO₂ concentration (C_i) decreased with different degrees. (2) The activities of antioxidases (Peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT)) in the leaves and roots of Z. jujube enhanced after treatment with low concentration of H₂O₂ (≤ 0.08 mmol/L), and the activities of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), sedoheptulose-1,1-bisphosphatase (SBPase), and fructose 1,6-diphosphate aldolase (SBPase) in the leaves increased significantly by 38.24%, 42.15%, and 84.08%, respectively. However, there was no significant change for the activity of transketolase (TKase). (3) The maximal photochemistry efficiency (F_v/F_m), actual photochemistry efficiency (ΦPSⅡ), photochemical quenching coefficient (qP), and the share of absorbed light energy for photochemical reactions (P) in the leaves of Z. jujube increased by 37.52%, 135.95%, 53.10%, and 98.36% respectively under the treatment of H₂O₂. The PSⅡ non-photochemical quenching coefficient (NPQ), regulatory energy dissipation Y (NPQ), non-regulatory energy dissipation Y (NO), the proportion of absorbed light energy used for antenna heat dissipation (D), the proportion of non-photochemical dissipation of PS II reaction center (E_x), and the unbalanced deviation coefficient of excitation energy distribution between two optical systems (β/α-1) decreased by 34.13%, 35.15%, 30.26%, 35.52, 32.30%, and 53.43%, respectively. The mitigate effect was significant, but the mitigation effect tended to decline with the increase of exogenous concentration of H₂O₂. Comprehensive analysis showed that the mitigate effect of H₂O₂ on cadmium toxicity of Z. jujube was related to many physiological processes, such as improving photosynthesis of Z. jujube, maintaining the high activity of antioxidant system and improving photochemical efficiency of PS II. Among them, 0.08 mmol/L H₂O₂ was the best way to improve the repair efficiency of Z. jujube, which could be used as a strengthening measure of phytoremediation.