Abstract: The prestressed concrete cylinder pipes (PCCPs) are often deteriorated due to rupture of prestressed steel wires. Such deteriorated PCCPs need to be retrofitted timely and effectively, otherwise they could suffer from explosion. An innovative retrofitting technique is therefore proposed, which is carbon fiber reinforced polymer (CFRP) wrapping outside the deteriorated PCCPs, and the retrofitting technique is especially suitable for the cases that shutting off water is impossible. In order to evaluate the effectiveness of the newly-proposed retrofitting technique for PCCPs, a full-scale PCCP of 2.8 m in inner diameter is tested under internal water pressure. The strains of PCCP structures are compared before and after the repair. It is found that the strains near the ruptured steel wires significantly decrease due to the presence of CFRP, which improves the operation of the PCCPs.