Sulphurous acid derived from sulfur dioxide (SO2) emission leads to the pollution of irrigation water and the inhibition of plant growth. The safe concentration threshold of NaHSO3 in plants should be clarified to promote agricultural production. In this study, Orychophragmus violaceus seedlings were used as experimental materials and five NaHSO3 concentrations (i.e., 0, 1, 2, 5, 10 mmol center dot L-1) were simultaneously sprayed on the leaf surface of different seedlings separately. Leaf physiology responses under different concentrations were analyzed. The NaHSO3 did not promote photosynthesis in O. violaceus under the 1 and 2 mmol center dot L-1 treatments. It was conducive to the net photosynthetic rate (P-N), photorespiration rate (R-p), chlorophyll content, actual photochemical quantum yield (Y-II) and photochemical quenching (qP) under the 5 mmol center dot L-1 treatment. However, quantum yield of regulated energy dissipation (Y-NPQ) and nonphotochemical quenching (NPQ) were inhibited. Under the 10 mmol center dot L-1 treatment, P-N, chlorophyll content, Y-II, qP, dark respiration rate (R-d) and electron transport rate (ETR) showed significant decreases, while the photorespiration portion (S-p) significantly increased. Our results demonstrated that NaHSO3 provided a sulfur source for plant growth and interfered with the redox reaction of the plant itself, and its role as a photorespiratory inhibitor might be masked.