Objective To evaluate the prognostic factors of poor prognosis in children with acute myocarditis. Methods 182 children with acute myocarditis in our intensive care unit (ICU) were divided into three groups according to their prognosis: the full recovery group(group A, n=109), the no full recovery group(group B, n=37), the death group (group C, n=36). The clinical data, laboratory data, echocardiographic data and electrocardiogram data were collected and compared. The medication history and nursing plan were collected and the predictors of mortality or incomplete recovery were evaluated. Results The left ventricular end-diastolic diameter z score (OR=1.252, 95%CI 1.005~1.560, P=0.047), extracorporeal membrane oxygenation (OR=9.843, 95%CI 1.045~92.765, P=0.047) Adrenaline use (OR=18.553, 95%CI 1.758~195.706, P=0.016) were important predictors of mortality. Left ventricular end-diastolic diameter z score (OR=1.361, 95% CI 1.067~1.735, P=0.014) was an important predictor of incomplete recovery. Conclusion Left ventricular dilatation at diagnosis reflects severe myocardial injury in the acute phase. If the diagnosis of acute myocarditis results in left ventricular dilatation, the children should be closely monitored to avoid exacerbations and appropriate treatment to avoid poor prognosis.