Abstract: Though Korea has established and operates a variety of urban infrastructure under the name of U-City, it has failed to unify infrastructure operations, which can be considered the biggest difference between existing city and U-Cities. In light of the growing need for active maintenance, there is a need to improve both the simple historical management and passive post-management. The aim of the study is to suggest algorithm not only for unified operation but also for preventive maintenance of U-City facility. The methods of study are as follows. First, the improvement of infra maintenance was deduced by analyzing the maintenance condition and the existing material of Dongtan U-City. Second, the systematic DB establishment was deduced by considering infra life cycle for preventive maintenance. Third, the importance level of the infra was deduced based on both the public interest and residents' opinion in Dongtan. Lastly, the final maintenance algorithm was deduced, considering the above deductions. The infra maintenance algorithm this study suggests is available at the field immediately in Dongtan and accepted in other U-City areas as well. It means that the algorithm can serve as a basis of preventive maintenance in U-City infrastructure.