Objective: To study the effect of simvastatin on mRNA expression of inflammatory cytokines, including TNF-α,IL-1β, IL-6, and IL-10, after myocardial infarction (MI) in rats. Methods: The experimental rats were divided into three groups: Sham operation group (Sham), the rats were performed a left thoracotomy with no ligation of left descending coronary artery (LAD); Myocardial infarction control group (MI-C), the rats were performed a left thoracotomy with ligation of LAD; Simvastatin group (MI-S), the rats were performed a left thoracotomy with ligation of LAD, and given simvastatin 40 mg/kg body weight per day through gavage, while the other two groups were given equal normal saline by gavage. All animals were caged to feed four weeks. After finished, the rats were killed, and the hearts were harvested and cut into two equal parts at the level of the papillary muscle: one was used to determine mRNA expression of myocardial cytokines by RT-PCR, and the other was used to measure cytokines by Western blotting and immunohistochemical staining. Results: All the pro-inflammatory cytokines mentioned above showed few expression in Sham operation group. In the MI groups(including MI-C and MI-S groups), mRNA expression of each of these cytokines markedly increased compared with the Sham operation group ( P ＜ 0.01). Compared with MI-C group, the mRNA expression of TNF-α, IL-1β and IL-6 in the MI-S group significantly reduced( P ＜ 0.01), and mRNA expression of IL-10 obviously increased ( P ＜ 0.01). Cytokines principally located in cardiomyocytes of non-infarcted area and survived cardiomyocytes of infarcted area, simvastatin could decrease TNF-α, IL-1β, and IL-6 and increase IL-10 by confirmation of immunohistochemical staining. Conclusion: Simvastatin markedly lowers pro-inflammatory cytokines, and increases inflammatory protective cytokine. Its mechanism needs to be elucidated.