To study the effects of water extract of Aspongopus chinensis Dallas on cell proliferation and cell cycle of SGC-7901 and HepG2cell lines,by using inverse microscopy,the morphology of the cells were observed.The antiproliferative effects of water extracts were assessed by MTT assays.The cell cycle was measured by flow cytometry.The results showed that after being treated with water extracts,cells grew round,and the intercellular space were increased,cell fragmentation were increased and cells were against the wall in the inverse microscopy.The water extracts could inhibit the proliferation of SGC-7901 and HepG2 cell lines in a dose-dependent manner.SGC-7901 and HepG2 cell lines were sensitive to water extract with an IC50 values of 154.24mg/L and 129.46mg/L,respectively.From the result of flow cytometry analysis,water extract,as compared with the untreated cells,caused significant increase in cell ratio at the S and G2/M phases,and anreduction in cell ratio at the G0/G1 phases.The water extract could inhibit proliferation of both cancer cell in vitro,and especially arrest cancer cells at the S phase of the cell cycle for SGC-7901 and HepG2cell.