Abstract: In this study, 2-year-old Quercus robur saplings were used as experimental materials to investigate the effects of varying levels of salt stress on their photosynthetic physiological characteristics. Eight treatment gradients were established: CK (control), 0.2% (T_0.2), 0.4% (T_0.4), 0.6% (T_0.6), 0.7% (T_0.7), 0.8% (T_0.8), 0.9% (T_0.9), and 1% (T₁). The results showed that under the T_0.2 treatment, salt stress had minimal impact on the growth and photosynthetic physiological and ecological characteristics of Quercus robur. As salt concentration increased, the net photosynthetic rate (P_n) and stomatal conductance (G_s) of the leaves decreased significantly compared to CK, while the intercellular CO₂ concentration (C_i) increased. This suggests that the reduction in P_n under salt stress is primarily due to non-stomatal factors. During the light response process, low levels of salt stress had a minor effect on the net photosynthetic rate, whereas high levels of salt stress had a significant impact. The salt tolerance threshold for Quercus robur was determined to be 0.36% NaCl, indicating that it can be cultivated and planted in mildly saline soils.