Objective：To investigate the distribution pattern of 99mTc-AcTnIMA in rats with experimental acute myocardial injury, and to determine the possibility of 99mTc-AcTnIMA to be a tracer of myocardial radioimmunoimaging for the detection of myocardial injury. Methods：In the experimental group，20 rats with acute myocardial lesion were injected with 0.2mci 99mTc-AcTnIMA, and killed 2, 4, 6 h and 8 h after injection respectively（5 rats）. Blood, liver, spleen, kidney, healthy muscle, lung and heart muscle of each rat were taken and the injected dosage（ID％／g） and the ratio of ID％／g for heart to lung（HLR） was calculated. In the pharmic control group，20 rats with acute myocardial lesion were injected with 0.2mci 99mTc-N-IgG and were killed in the same way as the experimental group. Lungs and hearts were taken and ID％／g and HLR of each rat was calculated. In the blank control, 20 healthy rats were injected with 0.2mci 99mTc-AcTnIMA and the subsequent procedures were same as the pharmic group. Results：Specific uptake of 99mTc-AcTnIMA by acute compromised cardiac muscles was observed with its peak 4 h after injection. Conclusion：99mTc-AcTnIMA could be a useful tracer of myocardial radioimmunoimaging to diagnose acute myocardial injury.