The majority of contaminated areas are polluted with multiple pollutants. It is a major challenge for environmental and ecological scientists to investigate the interactions between and combined effect of such pollutants. The complexity of regional ecosystems makes research of combined contaminants very difficult, and also makes it difficult to perform regional ecological risk assessment. The microcosm tests were conducted to explore the separate and combined effects of 2,2 ', 4,4' - tetrabromo diphenyl ether (BDE-47) and decabromodiphenyl ether (BDE-209) on Daphnia magna with several endpoints as immobilization, reproduction rate, mortality rate, heart rate, of ChE and GST, CAT enzyme activity, etc. after 48h and 21d exposure. A Daphnids-Springtail Ecological Risk Model (DSM) was developed to assess the regional ecological risk, based on the result of microcosm daphnids tests and the literature data of springtail. This model was applied to evaluate the ecological risks of PBDEs on the Yangtze River Basins of Chongqing, with comparison of the application of Relative Risk Assessment Model (RRM) in the same area, in order to certify its advantages and restrictions. The results showed that, after acute exposure (48h), the EC50 value ofBDE-47 on the immobilization of D. magna was 112.5μg/L. The heart rate of D. magna was not affected significantly by BDE-47. In contrast, the heart rate of Daphnids was significantly increased by BDE-209, while no effect on immobilization of D. magna was shown. The antagonistic effects on immobilization of D. magna and the synergistic effects on the heart rate of Daphnids were shown with the combination exposure of BDE-47 and BDE-209 in 48h. The antagonism was with the increase of BDE-209 concentration. In chronic exposure tests (21d), the survival and reproduction on D. magna were significantly affected by BCD-47. ChE, GST activities of maternal daphnids was inhibited by BDE-47, but the inhibition rate was not high. CAT activity of maternal daphnids was significantly induced by BDE-47, and showed a dose-response relationship. The ChE and GST activities of maternal daphnids were significantly inhibited by BDE-209. BDE-209 significantly induced CAT activity, and in low concentrations showing a dose-response relationship. The antagonistic effects on the mortalities, reproductions and ChE activities of maternal daphnids were shown with the combination exposure of BDE-47 and BDE-209 in 21d. While the synergistic effects on GST activities of maternal daphnids were showed with the combination exposure of BDE-47, BDE-209. CAT activities of D. magna were first induced, then inhibited by BDE-47, BDE-209. A Daphnids-Springtail Model about regional ecological risk assessment (Daphnids the-Springtail model, DSM) was developed based on the above test data and combining with the springtail test data. Toxicity data, macroscopic study, land use types and other data were integrated into this model, with the application of multi-level biomarkers, for regional ecological risk assessment. This model makes the evaluating results closer to the actual situation. The DSM model was applied to assesse the ecological risk of PBDEs on the Yangtze River Basins of Chongqing in 2012. The results indicated that the highest relative score of risk area was in the flow area of ​​Chongqing city and in the downstream of the main city. The absolute risk value was the highest in city's main region. Relative Risk Model (RRM) was used to evaluate the ecological risk of Yangtze River basins of Chongqing in 2006 and 2010. The results showed that the relative risk value of the study area in 2010 was lower than that in 2006. The highest risk source changed from agricultural land in 2006 to urban and industrial land in 2010. The water quality had always been the highest risk endpoint.