To explore the potential of phytoremediation 2,4-dinitrophenol (2,4-DNP) by Salix babylonica, its physiological response to 2,4-DNP, and the effect of exogenous selenium (Se) addition on its physiological response were studied in hydroponics. The results indicate that an increasing concentration of 2,4-DNP decreased the plant net photosynthetic rate (P_n), transpiration rate (T_r), chlorophyll content and increased intercellular CO₂ concentration (C_i). Both concentrations of Se increased P_n and chlorophyll content and reduced C_i. At low concentrations of 2,4-DNP, Se addition reduced POD and SOD activity, whereas at high concentrations its effect was reversed. In conclusion, the non-stomatal factor was the main reason for 2,4-DNP inhibiting the photosynthesis of S. babylonica. The tolerance of S. babylonica to 2,4-DNP was strong when 2,4-DNP concentration is between 10 and 20 mg.L^-1. Adding low concentration Se (≤2 μmol.L^-1) can promote the photosynthesis of S. babylonica and enhance its tolerance to 2,4-DNP pollution.