Abstract: To investigate suppressing effects of flavonoids from the leaves of Acer truncatum in the activation od BV-2 microglia,cells were treated with flavonoid (5,10 ,15μmol/L) prior to LPS exposure,then the effects on the mRNA and protein levels of pro-inflammatory enzymes,inducible nitric oxide synthase (iNOS),cyclooxygenase-2 (COX-2),pro-inflammatory cytokines,tumor necrosis factor-α (TNF-α),interleukin-1β (IL-1β) and inflammatory signaling proteins nuclear factor-κB (NF-κB) were analysed by RT-PCR and double-immunofluorescence labeling assay.The results indicate that flavonoid has an effect on the expression of iNOS,COX-2,TNF-α,IL-1β and NF-κB through transcriptional and translational inhibition.Therefore we think the flavonoid can restrain microglial cells activity by means of regulation pro-inflammatory mediators of BV-2 cells that induced by LPS,so it can exert anti-neuroinflammatory actions.