In the present study, a released exopolysaccharide (r-EPS1) from L. plantarum 70810 was modified by acetylation, phosphorylation and carboxymethylation. Scanning electron micrograph (SEM) and thermogravimetric analysis (TGA) showed the r-EPS1 derivatives had different surface morphology and thermal behavior. Compared with r-EPS1, the derivatives exhibited stronger antioxidant and antitumor activities. The study provided experimental evidences that chemical modification could be an effective way to improve the bioactivity of exopolysaccharide from L. plantarum 70810. It is noted that these derivatives could be explored as novel potential antioxidant and antitumor agents.