Abstract: This study investigated the antioxidant activity and the inhibition effect of tumor cell proliferation of polysaccharides from the seeds of Cuscuta chinensis Lam. The scavenging rates of the polysaccharides on DPPH, hydroxyl and superoxide anion free radicals and total reducing power were evaluated. The inhibitory effect of the polysaccharides on the proliferation of A549, HepG2, PANC-1 tumor cells and human normal liver cell L-02, human normal fetal lung fibroblast HFL-1 cells were determined by MTT assay. Results showed that the IC₅₀ values of the polysaccharides for scavenging DPPH, hydroxyl, and superoxide radicals were 0.25 mg/mL, 0.36 mg/mL, and 0.18 mg/mL, respectively. The reducing power was 0.55 (OD₇₀₀), when the concentration of polysaccharides was 1.0 mg/mL. The IC₅₀ values on cytotoxicity were 137.6 μg/mL, 341.7 μg/mL, and 625.4 μg/mL for A549, HepG2, and PANC-1 cells, respectively. The polysaccharides were almost nontoxic to L-02 and HFL-1 cells as their IC₅₀ values (1.223 and 1.299 mg/mL for L-02 and HFL-1 cells, respectively) were much higher. At the 50% inhibitory concentration of A549, HepG2, and PANC-1 tumor cells, the survival rate of normal hepatocyte L-02 and HFL-1 was more than 90%, indicating that the polysaccharide could selectively inhibit the growth of tumor cells and rarely inhibit the growth of normal cells.