Objective To observe the Interference effects of siRNA(small interference RNA) intrathecal injection on the expression of mRNA and protein of MrgC, on PWTs (paw withdrawal thresholds) and the phosphorylation of PKCε Ser729 in ipsilateral DRG(dorsal root ganglion) of rats with chronic inflammatory pain induced by CFA(complete freund's adjuvant). Methods 16 health adult male SD (Sprague-Dawley) rats were randomly divided into 2 groups: control siRNA group and MrgC siRNA group, 8 rats in each group. After success of intrathecal catheterization, corresponding siRNA was injected in rats for 4d, once a day, 5μg/d per rat. The model of chronic inflammatory pain was established by CFA (0.1ml per rat) subcutaneously injected into the right hind paw at 4th day post-administration, then two groups were administrated corresponding siRNA on alternate day and executed at the 11th day post-administration. The PWTs were measured at 5 time points of pre-intrathecal catheterization, pre-administration, 4th day post-administration(0h post-CFA injection), 5th day post-administration(24h post-CFA injection), 11th day post-administration(7 d post-CFA injection). The expression of MrgC mRNA in ipsilateral DRG was detected by fluorogenic quantitative PCR, and the expression of MrgC and the phosphorylation of PKCε Ser729 in ipsilateral DRG was detected by immumofluorescence method. Result Compared with 4th day post-administration, PWTs of both two groups at 5th day post-administration decreased significantly (P<0.01). While there was no significant difference of PWTs between two groups at every detective time point. Compared with control siRNA group, the expression of MrgC mRNA and the rate of MrgC positive cells in MrgC siRNA group both decreased significantly (P<0.01,P<0.05), whereas the rate of p-PKCε Ser729 positive cells increased obviously (P<0.05) at 11th day post-administration. Conclusion MrgC siRNA can effectively interfere the expression of mRNA and protein of MrgC in L4-L6 ipsilateral DRGs of rats with chronic inflammatory pain induced by CFA, and the siRNA interference on MrgC can obviously up-regulate the phosphorylation of PKCε Ser729, while it has no significant effect on PWTs of rats.