Objective To evaluate the antibacterial activity in vitro of Galla Chinensis ethanol extractant(GCEE)against S.epidermidis,and the change of cell morphology of S.epidermidis.Methods Deterimination of antibacterial activity of GCEE against 124 strains S.epidermidis was performed by using agar dilution method,and the changes of cell merphalogy of S.epidermidis was examined by microscope.Results The MIC90 of GCEE against 43 strains of MRSE(methicillin-resistant staphylococcus epidermidis)and 81 strains of MSSE(methicillin-sensitive staphylococcus epidermidis)were 0.288 and 0.144 mg/mL respectively.Under microscope,the cells of S.epidermidis were expansion by degrees,with the edge of cell of S.epidermidis irregular.The substances in cells of S.epidermidis were disappear final.Conclusion Galla Chinensis ethanol extractant had strong antibacterial activity against 124 strains of S.epidermidis,and the cell morphology of S.epidermidis changed.