Digital twin technology is being rapidly applied and developed in the field of urban water security. Firstly, the paper sorted out and analyzed the current situation of digital twin technology applications for urban water security, explained the framework of urban water security system based on digital twins, and introduced the key techniques and capability requirements in the digital twin system from the perception and collection layer, infrastructure layer, data layer, model layer, knowledge layer, and application layer. Secondly, the application progress of digital twins in urban water security was reviewed, including flood control and disaster reduction, water resource conservation and intensive safe utilization, water ecological protection, and intelligent water conservancy engineering. The construction progress and application effectiveness of digital twin platforms for water conservancy projects in typical cities were introduced. Finally, the paper summarized the challenges faced by the in-depth application of digital twins in the field of urban water security and proposed prospects, aiming to provide a reference and guidance for the construction of urban water security capabilities that integrate digital twin technology.