Abstract: Erythrophleum fordii Oliv. seedlings were used as experimental materials to determine the physiological responses, based on photosynthetic pigment and soluble sugar indices, of differently treated seedlings to SNP-AlCl₃ interaction using two-factor completely randomized experiments. Results showed that chlorophylla, chlorophyllb, and carotenoid contents in leaves were the highest under Treatment 4 and the lowest under Treatment 9. However, MDA and free proline content in leaves demonstrated the opposite pattern. Soluble sugar and soluble protein content in leaves was the highest under Treatment 4 and the lowest under Treatment 9. Furthermore, SOD, POD, and CAT showed highest activity under Treatment 10 (0.8 mmol/L AlCl₃ and 0.1 mmol/L SNP). After the addition of SNP, the contents of chlorophylla, chlorophyllb, carotenoid, soluble sugar, and soluble protein in leaves of E. fordii seedlings and the activities of SOD, POD, and CAT were significantly higher than when SNP was not added. Based on correlation analysis, we found a significant positive correlation between total content of chlorophylla, carotenoid, chlorophyll, and soluble protein (P < 0.01). Our research suggests that low-concentration AlCl₃ (0.2 mmol/L) stress can facilitate E. fordii seedlings growth and exogenous addition of SNP can relieve the toxic effects of high-concentration AlCl₃ (0.8 mmol/L) stress to E. fordii seedlings. Thus, these results can be applied for cultivation and resistance research of E. fordii seedlings.