Objective: To evaluate the feasibility ofin vitro balloon dilatation for treating aortic coarctation infants younger than 6 months. Methods: A total of 13 aortic coarctation infants treated in our hospital from 2011-01 to 2015-12 were summarized. The patients were at the mean age of 3.4 months (from 20 days to 6 months), with the mean body weight of 4.8 kg (from 3.6 kg to 6.2 kg) including 9 male. Aortic coarctation segments were resected during the operation and the resected segments were expanded by percutaneous transluminal angioplasty (PTA) via (2-4) times diameter balloon dilatation. The diameters of resected aortic segments were recorded before and after expansion; the change of vascular middle smooth muscle layer was observed by HE staining. Results: There were 8 cases with non-restricted ventricular septal defect (VSD) and 3 of them received staging operation, 2 with atrial septal defect (ASD), 3 with bicuspid aortic valve, 3 with patent ductus arteriosus (PDA) and 1 with pericardial effusion. The resected aortic segments presented that 9 patients had diaphragm type narrow and 4 had tube type narrow. After PTA, the diameters of resected aortic segments were slightly increased for the mean of 0.2 mm and no obvious change was observed; HE staining showed that the vascular inner mucosa was shed, while the middle smooth muscle layer was intact. Conclusion: Balloon dilatation had the poor effect for treating aortic coarctation infants younger than 6 months; surgical procedure could be applied for treating the relevant patients.