Abstract: The aim of this study was to determine the effect of silicon on the antioxidant system and membrane stability of Saponaria officinalis under drought stress. Silicon was added to soil at four concentrations (0.1, 0.2, 0.3, 0.4 g/kg SiO₂) and the soil moisture content was adjusted to impose normal conditions, mild drought stress, and severe drought stress on S. officinalis. The protective enzyme activity, antioxidant content, malondialdehyde (MDA) content, and relative electrical conductivity of the leaves of S. officinalis were determined. The results showed that with increasing severity and longer duration of drought stress, the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), and the contents of reduced glutathione (GSH) and ASA (ascorbic acid) in the leaves of S. officinalis first increased and then decreased, and the MDA content and relative electric conductivity increased. Compared with the control, the treatments with silicon added to soil showed higher activities of SOD, POD, CAT (>30% higher) under drought stress, and lower MDA content and relative electrical conductivity (>25% lower), resulting in more stable GSH and ASA contents. These results indicated that silicon can effectively alleviate damage to S. officinalis cell membranes under drought stress by improving the performance of the antioxidant system. As the concentration of silicon increased, the drought resistance of S. officinalis increased gradually and then stabilized. The optimal concentration of SiO₂ in soil was 0.3-0.4 g/kg.