Objective:To investigate the chemical constituents of essential oil from Chenopodium ambrosioides fruit and study their antibacterial activities and inhibitory effects on HepG2 cell proliferation.Method: Essential oil of C.ambrosioides fruit was extracted with steam distillation（SD） and chemical constituents of the oil extrated were analyzed by Gas Chromatography-Mass Spectrometry（GC-MS）;Continuous twifold liquid gradient dilution method and transfection method were employed to determine the antibacterial activity（MIC and MBC） and MTT assay was performed to observe the inhibitory effect of the essential oil on the proliferation of HepG2 cells.Result: There were 21 ingredients identified in the the essential oil from Chenopodium ambrosioides fruit

mainly including 7-Oxabicyclo heptan-2-one

6-methyl-3-（1-methyle-thyl）-（66.93%）

followed by 1-methyl-（1-methyl-alkenyl） Cyclohexene（15.67%） and o-methyl-isopropyl benzene（12.96%）.A good antibacterial effect of chenopodium ambrosioides fruit volatile oil was showed on white chain strains of bacteria

staphylococcus epidermidis

streptococcus A

streptococcus B and Proteus and a strong inhibitory effect on proliferation of human hepatoma HepG2 cells（P<0.01）.The IC50 for 48 h and 72 h was 0.034 1 μg·mL-1 and 0.069 μg·mL-1

respectively.Conclusion: The main ingredients of the essential oil from Chenopodium ambrosioides fruit are monoterpenes

with a good antibacterial effect and inhibition of the proliferation of HepG2 cells.