Cochlear implant (CI) is the only method for efficacious treatment of congenital severe deafness at present. However, for children with congenital severe deafness after CI, the mechanism of the structural and functional changes of their cerebral cortex is not clear. This study was based on the cross-modal reorganization of deaf patients. Event related potential (ERP) and source localization technique were used to visualize the change of cortical activity in children with congenital severe deafness during 1-year period (0, 1, 3, 6, 9 and 12 months after CI). We aimed to investigate the association between hearing restoration and cross-modal reorganization in children with congenital severe deafness after CI. The results showed that the cross-modal reorganization exists in children with congenital severe deafness. During hearing restoration, the function of the cross-modal reorganization reversed to the normal state. The method and conclusions of this study may be of significance in guiding the training and evaluation of hearing rehabilitation after CI in patients.