Background No-reflow after emergency percutaneous coronary intervention (PCI) for acute ST segment elevation myocardial infarction (STEMI) is related to the severe prognosis. The aim of this study was to evaluate the efficacy of Tongxinluo, a traditional Chinese medicine, on no-reflow and the infarction area after emergency PCI for STEMI.Methods A total of 219 patients (female 31, 14%) undergoing emergency PCI for STEMI from nine clinical centers were consecutively enrolled in this randomized, double-blind, placebo-controlled, multicenter clinical trial from January 2007 to May 2009. All patients were randomly divided into Tongxinluo group (n=108) and control group (n=111), given Tongxinluo or placebo in loading dose 2.08 g respectively before emergency PCI with asprin 300 mg and clopidogrel 300 mg together, then 1.04 g three times daily for six months after PCI. The ST segment elevation was recorded by electrocardiogram at hospitalization and 1, 2, 6, 12, 24 hours after coronary balloon dilation to evaluate the myocardial no-flow; myocardial perfusion scores of 17 segments were evaluated on day 7 and day 180 after STEMI with static single-photon emission computed tomography (SPECT) to determine the infarct area.Results There was no statistical significance in sex, age, past history, chest pain, onset-to-reperfusion time, Killip classification, TIMI flow grade just before and after PCI, either in the medication treatment during the follow up such as statin, β-blocker, angiotensin converting enzyme inhibitor (ACEI) or angiotensin receptor blocker (ARB) between two groups. There was significant ST segment restoration in Tongxinluo group compared to the control group at 6 hours ((-0.22±0.18) mV vs. (-0.18±0.16) mV, P=0.0394), 12 hours ((-0.24 ± 0.18) mV vs. (-0.18±0.15) mV, P=0.0158) and 24 hours ((-0.27±0.16) mV vs. (-0.20±0.16) mV, P=0.0021) reperfusion; and the incidence of myocardial no-reflow was also reduced significantly at 24-hour reperfusion (34.3% vs. 54.1%, P=0.0031). The myocardial perfusion scores of 17 segments evaluated by static SPECT was improved significantly on day 7 and day 180 after STEMI in Tongxinluo group compared to the control group (0.61±0.40 vs. 0.76±0.42, P=0.0109 and 0.51 ±0.42 vs. 0.66±0.43, P=0.0115, respectively).There was no significant difference in severe adverse events between two groups.Conclusion Tongxinluo as a kind of traditional Chinese medicine could reduce myocardial no-reflow and infarction area significantly after emergency PCl for STEMI with conventional medicine therapy.