Deformation happening in deep foundation pit excavation is a growing concern to underground construction, threatening not only the construction safety but also the adjacent environment. Traditional deformation monitoring is conducted once a day through the method of manual measurement. Such monitoring strategy has been blamed for inefficiency and error-prone, and also the monitoring results cannot be timely received by on-site managers for safety management. Therefore, the study proposes a digital twin-driven deformation monitoring system to support accurate risk-preventing decisions. The proposed system comprises four interconnected components for data acquisition, data processing, result visualization, and risk warning, respectively. A real-life tunnelling construction project – Lianghu tunnelling construction in Wuhan, China – is used to illustrate the functionality of the proposed system. Findings show that the system will be a valuable step for implementing digital twin to deep foundation pit excavation from concept to practice.