【Abstract】Objective To explore the dexmedetomidine anti-inflammatory effect in attenuating hypoxia reoxgenation injury of H9C2 cells. Methods Rat cardiomyocyte cell line H9C2 cells were cultured in vitro, and Na2S2O4 was used to establish the hypoxia and reoxygenation injury model on H9C2 cells. Cultured H9C2 cells were divided into three groups: normal control group(group C), the cells were cultured as usual; hypoxia and reoxygenation group (group H/R), the cells were subjected to 1h hypoxia induced by 4mM Na2S2O4, then followed by 12h reoxygenation by replaced the normal media; dexmedetomidine preconditioning group(group D), dexmedetomidine at various concentrations (0.1μM、1μM、10μM) was performed prior to Na2S2O4-induced H/R injury, the rest of the steps are essentially the same as the H/R group. The cell survival rate (MTT) and LDH activity were detected after treatment, the cellular morphology was observed by inverted miscroscope, the TNF-α、IL-6、IL-1β mRNA expression were detected by RT-PCR . Results Compared with group C the cell survival rate of group H/R decreased to 44.08%(p<0.01), LDH activity increased significantly (p<0.01); compared with group H/R, the cell survival rate and LDH activity of the group D were improved, dexmedetomidine at 1μM concentration preconditioning significantly restored cell viabilitiy to 75.21% (p<0.05) and reduced the activity of LDH significantly (p<0.05). The condition of cell necrosis, irregular cell arrangement, and the decline of cell membrane refractive index caused by H/R injury can be partly reversed by dexmedetomidine. Compared with group C, the TNF-α、IL-6、IL-1βmRNA expression level of group D and group H/R increased significantly; Compared with group H/R, the TNF-α、IL-6、IL-1β mRNA expression levels of group D decreased significantly (p<0.05). Conclusion Dexmedetomidine preconditioning attenuates hypoxia and reoxygenation injury of H9C2 cells, the mechanism may be related to inhibiting inflammatory reaction.