The location and ischemia extent are two important parameters for evaluating the acute myocardial ischemia (AMI). A focused-transducer-based photoacoustic imaging method was employed to assess time-dependent AMI. Our preliminary results show that the photoacoustic signal could identify the myocardium. The intensity and area of photoacoustic images of myocardium could be used for characterizing the ischemia extent and scope of myocardial ischemia. The results also imply that the intensity and area of photoacoustic images are the rapid fall of an exponential model with an increase of delaying time after the left anterior descending coronary artery (LAD) occlusion. These experimental results were consistent with the clinical characteristics. The findings suggest that the photoacoustic imaging be a potential tool for the real-time assessment of acute myocardial ischemia during surgical operation.