Objective: To investigate the cardiotoxicity indexes in children with malignant tumors after the administration of anthracycline (ANT) chemotherapy. Materials and Methods: Data from 131 children with malignant tumors who were treated using ANT chemotherapy at our hospital from January 2011 to December 2015 were collected to analyze the serologic indexes (such as N-terminal pro-brain natriuretic peptide [NT-proBNP] and isoenzyme of creatine kinase [CK-MB]) and changes in corrected QT interval(QT-c) and left ventricular ejection fraction (LVEF) before and after treatment with different ANT cumulative doses. Results: General clinical data revealed that 2 of the 131 children developed clinical cardiotoxicity. The ANT cumulative dose range was 12-697 mg/m(2). All patients were divided into three groups according to the ANT cumulative dose: group 1 (<100 mg/m(2)), 2 (>= 100 and <200 mg/m(2)), and 3 (>= 200 mg/m(2)). Although NT-proBNP and LVEF among the three groups differed significantly after chemotherapy (p = 0.022 and 0.035, respectively), no significance was noted for CK-MB and QT-c among the three groups after chemotherapy (p = 0.190 and p = 0.084, respectively). Multiple linear regression analysis revealed that the ANT cumulative dose had the most significant impact on NT-proBNP (standardized coefficient 0.423, p = 0). Pearson correlation analysis revealed that ANT cumulative dose was positively correlated with NT-proBNP post-treatment (correlation coefficient 0.423), but LVEF was negatively correlated with NT-proBNP after chemotherapy (correlation coefficient -0.542). Conclusions: NT-proBNP showed significant changes when the ANT dose was >200 mg/m(2). Post-treatment serum NT-proBNP was linearly correlated with ANT cumulative dose, hence strictly controlling the ANT cumulative dose and monitoring serum NT-proBNP may have certain clinical significance in predicting cardiotoxicity.