The aim of this study was to explore B-type natriuretic peptide (BNP) level expression of child patients suffering from ventricular septal defects (VSD) and analyze the relationship between BNP and cardiac function and heart failure (HF). Ninety-two pediatric patients with VSD treated at our hospital from October 2012 to September 2014 were enrolled in this study. They were divided into three groups: the no HF group (N.=30), the mild HF group (N.=31) and the moderate/severe HF group (N.=31), based on their scoring in the New York University Pediatric Heart Failure Index (NYU PHFI). Thirty-two healthy children attending our institution over the same period were enrolled as a control group. Venous blood samples were collected to test serum BNP level and left ventricular ejection fraction (LVEF), LVEF shortening (LVEFS), Left Ventricular End-Diastolic Dimension Index (LVEDDI) and Cardiac Index (CI) of all children. In VSD patients, serum BNP and LVEDDI levels were significantly higher than those in the control group, while LVEF, LVEFS and CI were significantly lower (P<0.05). HF severity was observed to be directly proportional to BNP and LVEDDI levels, but inversely proportional to LVEF, LVEFS and CI (statistical significance, P<0.05). Serum BNP content was negatively correlated to LVEF, LVEFS and CI (r=-1.142, -1.171 and -1.156, respectively; P<0.05), but positively correlated to LVEDDI and HF (r=0.134 and 1.143, respectively; P<0.05). Serum BNP levels pediatric VSD patients was in linear correlation with the Cardiac Index, and positively correlated to HF. This is significant in terms of diagnosis, treatment and prognosis of HF.