OBJECTIVE： To study the effects of mifepristone on the expression of inflammatory factors in endometriosis （Ems） model rats. METHODS： SD rats were randomly divided into normal group （normal saline）， model group （normal saline）， mifepristone low-dose， medium-dose and high-dose groups [0.65， 1.30， 2.60 mg/（kg·d）]， with 10 rats in each group. Except for normal group， Ems model was induced in other groups， and they were given relevant medicine intragastrically for consecutive 4 weeks. The volume of the ectopic focus was compared before and after treatment. The serum contents of TNF-α， IL-6 and IL-8 were detected by ELISA method. The phosphorylation of NF-κB p65 and the expression of COX-2 and PGE2 were detected by Western blot. The expression of NF-κB p65 mRNA in ectopic focus was detected by RT-PCR. RESULTS： Compared with normal group， the volume of the ectopic focus， the serum contents of TNF-α， IL-6 and IL-8， the expression of COX-2 and PGE2 protein， the phosphorylation of NF-κB p65 and the expression of NF-κB p65 mRNA in ectopic focus were increased in model group （P＜0.01）. Compared with model group， the volume of the ectopic focus， the serum contents of TNF-α， IL-6 and IL-8， the expression of COX-2 and PGE2 protein， the phosphorylation of NF-κB p65 and the expression of NF-κB p65 mRNA in ectopic focus were decreased in mifepristone groups （P＜0.01）， in dose-dependent manner. CONCLUSIONS： Mifepristone can reduce the volume of the Ems ectopic focus， via blocking NF-κB signaling pathway and reducing the expression of inflammatory factors.