Abstract: OBJECTIVE To elucidate the mechanism of anti-inflammatory effect of the essential component of Huanglian Jiedu decoction(HLJD) in vitro. METHODS RAW264·7 cells and J774A.1 cells were allocated to blank control group, model group (treated with LPS) and HLJD groups (treated with berberine, wogonin, baicalein and jasminoidin, respectively). After being treated with HLJD for 2 h and then incubated with LPS for 24 h, ELISA was used to detect the level of TNF-α, IL-6; mRNA expression of COX-2 was examined by RT-PCR, and COX-2 protein expression in cells was analysed by Western blot. RESULTS HLJD remarkably reduced TNF-α, IL-6 and COX-2 production in peritoneal macrophages elicited by LPS. CONCLUSION HLJD displays an anti-inflammatory effect mainly through inhibiting the production of inflammatory cytokines including TNF-α, IL-6 and COX-2.