OBJECTIVE：To study the imp rovement effects of 2-dodecyl-6-methoxycyclohexa-2，5-diene-1，4-dione（DMDD） from Averrhoa carambola on H 9c2 myocardial cell injury induced by high glucose and its mechanism. METHODS ：H9c2 myocardial cells were divided into normal group ，high glucose group ，osmotic pressure control group ，DMDD high ，medium and low concentration groups （8，4，2 μmol/L）. Normal group and high glucose group were treated with low glucose DMEM medium （containing 5.5 mmol/L glucose ，similarly hereinafter ） and high glucose DMEM medium （containing 33.3 mmol/L glucose ， similarly hereinafter ）for 48 h，respectively. The cells in osmotic pressure control group were cultured in low glucose DMEM medium containing 27.5 mmol/L mannitol for 48 h. In DMDD groups ，cells were cultured in high glucose DMEM medium for 24 h， and then in high glucose DMEM medium containing corresponding concentration of DMDD for 24 h. At the end of cell culture ，MTT metho d was used to detect the cell survival rate. The activities of ROS ， GSH-Px and LDH in cellsupernatant were detected by using related kits. ELISA assay was used to detect the levels of TNF-α and IL-6 in cell supernatant. Cell apoptosis was d etected by acridine orange/ethidium bromide （AO/EB）staining. Western blot assay was used to detect the expression of apoptosis related proteins （cleaved caspase- 3，Bcl-2，Bax）and the phosphorylation level of nuclear factor κB （NF-κB）/NF-κB suppressor protein α（IκBα）signaling pathway related proteins （NF-κB p65，IκBα）. RESULTS ：Compared with the normal group ，survival rate ，the activity of GSH-Px and protein expression of Bcl- 2 in high glucose groups were decreased significantly（P＜0.01）；the activities of ROS and LDH ，the levels of TNF-α and IL-6，the protein expression of Bax and cleaved caspase-3，and the phosphorylation level of NF-κB p65 and IκBα were increased significantly（P＜0.01）；the cells showed orange yellow fluorescence ，and the number of cells with fuzzy morphology increased significantly ，showing an obvious apoptotic state. There was no statistical significance in above indexes of osmotic pressure control group compared with normal group. Compared with high glucose group ，the activities or levels of above indexes （except for cell survival rate an LDH activity in low concentration group ）were reversed significantly in DMDD groups （P＜0.05 or P＜0.01）；the orange yellow fluorescence in the cells decreased significantly ，and the cell morphology was relatively complete. CONCLUSIONS ：DMDD can significantly improve H9c2 myocardial cell injury induced by high glucose ；the mechanism of which may be associated with suppressing oxidative stress and inflammatory response ，regulating the expression of apoptosis related protein and NF-κB/IκBα pathway related protein.