Objective To investigate the protective effects of alpha-lipoic (α-LA) on H9c2 cardiomyocytes under-going hypoxia or hypoxia/reoxygenation(H/R) injury and explore its possible mechanisms. Methods H9c2 car-diomyocytes in hypoxia or H/R injury researches were respectively divided into normal control group, hypoxia or H/R group, hypoxia or H/R + α-LA group (LA group), hypoxia or H/R+α-LA + Daidzin group (Daidzin group) and hypoxia or H/R+α-LA +DMSO group ( DMSO group) . The myocardial cell survival was detected by MTT,the activity of LDH and ALDH2 were respectively analyzed by microtitration and ELISA,the MDA level was measured by TBA. Results Compared to the normal control group, the cell survival rates of hypoxia and H/R group were decreased ( P<0. 01 ) , the levels of MDA and LDH were significantly increased ( P<0. 01 ) . Compared to the hypoxia or H/R group, the cell survival rates and ALDH2 activities of LA group were improved (P<0. 05), the levels of MDA and LDH were decreased (P<0. 01). Compared to the LA group and DMSO group, the cell survival rates and ALDH2 activities of Daidzin group were decreased ( P<0. 05 ) , the levels of MDA and LDH were increased ( P<0. 05 ) , and no significant differences of all the above measures were found between LA group and DMSO group ( P>0. 05 ) . Conclusion α-LA can protect H9 c2 cardiomyocytes from hypoxia or H/R injury by means of upregulating activities of ALDH2 and decreasing hypoxia or H/R induced lipid peroxidation.