Abstract: To investigate the effect of extracellular polymeric substances of Scytonema javanicum(EPS) on apoptosis of A431 cells and the expression level of relative genes,cell viability was measured by MTT method,morphologic changes were observed by hematoxylin and eosin staining and transmission electron microscopy,DNA damage was detected by single cell gel electrophoresis(SCGE/comet assay),the expression level of caspase-3,bcl-2 and bax were detected by immunohistochemical staining.EPS significantly inhibited the proliferation of the A431 cells and the inhibitory effect was dose-and time-dependent,which was accompanied by the appearance of morphologic characteristics of apoptosis.The IC50 of A431 cells is 4.25mg/mL after the treatment of EPS for 96h.After 6 mg/mL EPS treatment for 48h,the DNA damaged seriously in A431 cells when compared with the untreated controls.The expression level of caspase-3 and bax were up-regulation while bcl-2 was down-regulation after 6mg/mL EPS treatment for 72h when compared with the untreated controls respectively.It concluded that EPS may inhibit the proliferation and induce apoptosis of A431 cells,in which caspase-3,bcl-2 and bax were involved.