To observe the influence of neuregulin-1 on the cardiac function of post-myocardial infarction rats. Methods Left ventricular MI was created in Sprague-Dawley rats by ligation of the left anterior descending coronary. Six months after the operation, rats were evaluated with echocardiology methods. 36 rats that had an infarct area and a EF around 60% were randomized into 3 groups: MI group(n=12) were injected a blank vehicle fluid intravenously for 5 days, after which they continued to be raised on standard food and water for 30 days. MI+NRG group(n=12), received NRG-110μg·kg-1 intravenously for 5 days, after which they continued to be raised on standard food and water for 30 days. MI+Capt group (n=12) received captopril orally (dissolved in their drinking water 2g/L) for 30days, after which tap water substituted the solution for 5 days. Final echocardiographic and hemodynamic measurements were made at the end of 1 month of therapy. Total RNA was extracted from frozen left ventricular tissues, and was reverse transcribed into firststrand PCR was performed with primers for BNP、 ANP. Results Rats treated with neuregulin had a smaller LVDs (P=0.014), a betterLVEF (P=0.004),and a tendency towards less lung perfusion than untreated rats. Neuregulin decreased the expression of ANP mRNA in the ventricle (P=0.025).Conclusion Neuregulin markedly improved the cardiac function of rats that survived myocardial infarction,and decreased the expression of ANP mRNA in the ventricle.