This study aimed to optimise the conditions for fermentation of exopolysaccharide (EPS) produced by a space-induced Lactobacillus plantarum SS18-119,and further aimed to investigate the antioxidant activity of EPS produced by this strain.Using a single-factor,multi-level trial and an orthogonal test,the conditions for fermentation of EPS produced by the strain SS18-119 were optimised as follows:initial pH of the medium 7.0;fermentation temperature 37 °C;fermentation time 20 h;inoculation amount 3%.Under these conditions,the yield of EPS was 2.24 g/L,which was 1.19 times higher than that before optimisation.The scavenging rates of DPPH and superoxide anion radicals,Fe²⁺ chelating capacity,and overall reducing power of EPS at different mass concentrations were analysed under these fermentation conditions.The results showed that when the concentration of EPS was 2 mg/mL,the scavenging rate of DPPH radicals was 85.6%.At 10 mg/mL EPS,the scavenging rate of superoxide anion radicals was 79.0%,Fe²⁺ chelating capacity was 36.3%,and absorbance value of overall reducing power was 0.560 3.The results demonstrate that the space-induced L. plantarum SS18-119 can produce EPS at high levels under optimised fermentation conditions,and the produced EPS have strong antioxidant activity,providing a practical basis for the development of foods with antioxidant function.