Current studies on the toxicity of chemicals have focused on one step exposure, but the pollutant accumulation in the soil is gradual. A comparison of one step exposure and repeated exposure is needed to fully evaluate the actual toxicity of chemicals. In this study, we compared the bioaccumulation of decabromodiphenyl ethane (DBDPE) and biomarkers responses of Eisenia fetida in the one step exposure (spiked soil with 100 mg kg−1 DBDPE) and repeated exposure (DBDPE concentrations in the soil gradually adding from 25 to 50, 75 and 100 mg kg−1). Results show that repeated exposure decreased the bioaccumulation of DBDPE by 56.13%, but resulted in more severe damage to the epidermis and intestines surface. Two treatments both increased ROS levels and coelomocytes’ apoptosis rates, while only repeated exposure showed a recovery of these two biomarkers. After 28 days, TRIAP1, CAM, ATP-6 and NADH1 were differently regulated between the two treatments. In repeated exposure, habituation of earthworms to DBDPE caused biomarker responses closer to CK, while severe tissue damage suggested that the cumulative toxicity of DBDPE could not be eliminated through progressive environmental leakage. This study demonstrates that exposure patterns could affect the bioavailability and biotoxicity of pollutants in the terrestrial system.