Abstract: The main ingredient of extractable petroleum ether of Polyrhachis vicina Roger (EPPR) is octadecene unsaturated fatty acids. Mounting evidence supports that N-3 polyunsaturated fatty acids can attenuate neuroinflammation, reduce oxidative stress, then protect neurons. In order to explore the effect of EPPR on the inflammatory response of depressed rats, the model of depression was established by chronic unpredictable mild stress (CUMS). Sucrose preference test, forced swimming test were employed to investigate the anti-depressive effect of EPPR in rat. The activation of glial cells and astrocytes in the prefrontal cortex of depressed rats was observed by immunofluorescence. The levels of inflammatory factors were measured by Quantitative Real-time PCR. NF-κB was detected by immunoblotting. EPPR could significantly improve the depressive behavior of rats, decrease NF-κB translocation to the compartment of nucleus, down-regulate the pro-inflammatory cytokines IL-1β, TNF-α and indoleamine 2,3-dioxygenase (IDO) gene expression levels, inhibit the activation of microglia and astrocytes in depressed rats. These results suggest that EPPR could notably ameliorate inflammation induced by chronic stress, and the protective effect might be linked to the regulation of NF-κB p65.