Abstract: In order to explore the effect of polysaccharide of Gracilariopsis lemaneiformis (PGL) on cell proliferation activity and morphology of lung cancer cells,lung cancer cell line A549 was treated with PGL at various concentrations for 24,48 and 72 h respectively.The effects of PGL on cell proliferative activity,survival rate,morphology changes and apoptosis were investigated by CCK-8,trypan blue staining,DAPI staining,Annexin V-FITC/PI double staining and flow cytometry.Results showed that with the increase of the PGL concentration and time,cell proliferation ability and the survival rate decreased,the inhibition rates were gradually increased,especially in 50 μg/mL PGL for 72 h (P<0.01).Cell morphology has changed irregularly,the nucleus was damaged and cells were induced apoptosis,after 72 h these changes were more apparent.Overall studies have shown that PGL can inhibit lung cancer cell proliferation ability,reduce the cell vitality,change the cell morphology,induce cell apoptosis,and these effects were associated with time-concentration dependence.The mechanisms of antitumor activity of PGL were the outcome of multiple actions combined.