Biochemical responses of earthworm (Eisenia fetida) to fluoranthene were studied and cited as biomarkers for monitoring PAHs-contamination of sublethal concentration in the soil.Earthworms were exposed to soils contaminated with different concentrations of fluoranthene (60,120,240,480,960μg kg^-1 and CK).After exposure for 1,3,7 and 14 days,earth-worms were collected for analysis of contents of total cytochrome P450 and MDA and the activities of glutathione-Stransferase(GST),superoxide dismutase (SOD),peroxidase (POD) and catalase (CAT) in the guts.Results indicate that within the range of concentrations in the test,fluoranthene triggered varying responses from biochemical enzymes in the guts of the earthworms,particularly from P450 in content,and from SOD and POD in activity but not as significantly from GST,CAT and MDA.The research also revealed that the effect of duration of the exposure was stronger than that of dosage limited within the range of sublethal concentrations on the biochemical responses.As biochemical sensitivity to the pollutant varies from enzyme to enzyme,it is necessary to use a combined multitime multi-index diagnostic method in diagnosing ecotoxicity of the pollutant in soil,with special stress on sensitivity and effectiveness of the indicators of exposure to the pollutant.