Abstract: AIM: To observe the influence of cell apoptosis-related protein Bcl-2 family on H2O2-treated cardiac myocytes from neonatal rats by bone mesenchymal stem cells (BMSC). METHODS: Cardiac myocytes from neonatal rats were cultured and divided into three groups: control group, model group and BMSC-treated group. Transwell inserts were used for setting up co-culture system between cardiac myocytes and BMSC. MTT colorimetry was used to detect the cellular survival rate separately at 12, 24 and 48 h. Expression of cell apoptosis protein including Bcl-2 and Bax was examined by Western blot. RESULTS: Twelve hours after H2O2 treatment, the cell survival rate in model group was lower than in control group (P<0.05). There was no difference between model group and BMSC-treated group. Cellular survival rates of model group and BMSC-treated group were significantly different at 24 and 48 h. Twelve hours after H2O2 treatment, no difference was found in the expression level of Bax and Bcl-2 among the three groups. Bax expression in BMSC-treated group was significantly down-regulated at 24 h compared with model group (P<0.05). Although Bcl-2 expression was altered, there was no statistically significant difference. CONCLUSION: BMSC decrease myocyte apoptosis after damage from oxygen-derived free radicals, which may result from the down-regulation of Bax expression.