AIM: To investigate the effects of stress on the opening of mitochondrial membrane permeability pore (PTP) in rat heart and explore the possible molecular mechanism underlying PTP opening. METHODS: Stress animal model was established. After strained for differnet time, all rats were killed and PTP opening degree were examined by spectrophotometer. Bcl-2, Bax expression levels were determined by Western blot. RESULTS: Stress induced PTP opning, Bcl-2 expression inhibition and Bax level elevation in myocardial mitochondria. CONCLUSION: PTP opening was the important mitochondrial mechanism of stress-induced heart injury. Decrease in Bcl-2 expression and increase of Bax level may be an important molecular basis for PTP opening.