Diabetic peripheral neuropathy (DPN) is one of the most important complications in diabetes mellitus (DM), which has been reported to be modulated by long non-coding RNAs (lncRNAs). The purpose of the current study is to explore the regulatory mechanism of lncRNA HCG18 on DPN in vitro. The expression of lncRNA HCG18, miR-146a, TRAF6, CD11c, and iNOS was detected by qRT-PCR. Through Enzyme-linked immunosorbent assay, the levels of inflammatory factors (TNF-α, IL-1β, and IL-6) were determined. M1 macrophage polarization was measured by flow cytometry analysis. The interactions between miR-146a and HCG18/TRAF6 were predicted by Starbase/Targetscan software and verified by the dual luciferase reporter assay. Western blot assay was performed to determine the protein expression of TRAF6. LncRNA HCG18 was highly expressed in DPN model and HG-induced macrophages. The levels of inflammatory factors (TNF-α, IL-1β, and IL-6) were elevated in DPN model. The expression of M1 markers (CD11c and iNOS) was visibly up-regulated in DPN model and was positively correlated with HCG18 expression. LncRNA HCG18 facilitated M1 macrophage polarization. In addition, miR-146a was identified as a target of lncRNA HCG18. Overexpression of miR-146a reversed the promoting effect of HCG18 on M1 macrophage polarization. Simultaneously, TRAF6 was a target gene of miR-146a TRAF6 expression was positively modulated by HCG18 and was negatively modulated by miR-146a. Down-regulation of TRAF6 reversed the promoting effect of HCG18 on M1 macrophage polarization. LncRNA HCG18 promotes M1 macrophage polarization via regulating the miR-146a/TRAF6 axis, facilitating the progression of DPN. This study provides a possible therapeutic strategy for DPN.