Aim To investigate the biological distribution of ^99mTc-AcTnTMA-Fab in the SD rats with acute myocardial infarction. Methods ^99mTc-AcTnTMA was prepared and the rat model of acute myocardial infarction was built. Then 60 rats were randomized into experimental group，control group and blank group. There were twenty rats in each group. In the experimental group，20 rats with acute myocardial infarction were injected with 0.3 mCi ^99mTc-AcTnTMA-Fab and were killed 2 h，4 h，8 h and 12 h after injection respectively （5 rats）. Blood，liver，spleen，kidney，muscle，colon，lung and heart 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 control group，20 rats with acute myocardial infarction were injected with 0.3 mCi ^99mTc-AcTnTMA and were killed with subsequent procedure in the same way as the experimental group. In the blank group，20 normal rats were injected with 0.3 mCi ^99mTc-AcTnTMA-Fab and were killed with subsequent procedure in the same way as the experimental group. Results The value of ID%/g and HLR in the experimental group and the control group were significant higher than those in the blank group，which hinted that acute myocardial infarction could uptake specifically the ^99mTc-AcTnTMA-Fab and ^99mTc-AcTnTMA. The value of ID%/g and HLR in the experimental group was significant higher than those in the control group，which hinted that infarction tissue uptake of ^99mTc-AcTnTMA-Fab was more than^99mTc-AcTnTMA. Conclusions ^99mTc-AcTnTMA-Fab could be a useful tracer of myocardial imaging to diagnose acute myocardial infarction.