To explore the effect of dexmedetomidine (DEX) post-treatment on the inflammatory response of astrocyte induced by lipopolysaccharide (LPS). The astrocytes of neonatal mice were primarily cultured in vitro. After purification and identification, the cells were divided into five groups: group C: control group; group L: astrocytes were treated with 1 μg/ml LPS for 24 h; group D1, D2, and D3: astrocytes were pretreated with 1 μg/ml for 24 h LPS, and then cultured with low (0.1 μM), medium (1 μM), high (10 μM) concentration of DEX for 30 min, respectively. The cell survival rate was detected by cell counting kit. The expressions of inducible nitric oxide synthase (iNOS) mRNA, tumor necrosis gactor-α (TNF-α) mRNA, and interleukin-1β (IL-1β) mRNA were measured by RT-PCR in cell lysis solution of every group. The concentration of nitric oxide (NO) was detected by Griess method. The concentrations of IL-1β and TNF-α were measured, respectively, by enzyme-linked immuno sorbent assay. Compared with the group C, the expressions of iNOS mRNA, TNF-α mRNA, and IL-1βm RNA were significantly up-regulated, the release of NO, TNF-α, and IL-1β was significantly increased in group L (P < 0.05). Compared with group L, mRNA levels of inflammation-related factors and release of inflammatory factors were significantly down-regulated in group D2 and D3 (P < 0.05). There was no statistical difference between group D1 and group L. Pre-treatment with medium and high concentration of DEX can inhibit the LPS-induced inflammatory response of astrocyte.