Purpose: The purpose of this study was to determine whether a relaxing music was effective in reducing stress response of patients admitted to a coronary care unit with the diagnosis of acute myocardial infarction. Method: The research design was the chosen convenience sample of a randomized control group pre-posttest quasi-experimental design. Forty patients, 20 for an experimental group and another 20 for control group. The study was to provide the patients three different kinds of relaxing music. The experimental group listened to relaxing music for a 20-minute one time a day for 3days. The control group was just provided with a 20-minute period of rest. Test for hypothesis was done by repeated measured ANOV A. Result: The experimental group which received relaxing music showed a significantly lower level of electrodermal response, myocardial oxygen consumption and respiration rate, and a higher level of peripheral skin temperature than the control group. The experimental group which received relaxing music showed a significant reduction in state anxiety than the control group. Conclusion: The results showed that relaxing music is an effective nursing intervention for reducing physiologic and psychologic stress response of the patients with acute myocardial infarction in a critical intensive care unit.