To estimate the investment and benefits of the application of digital twins in the four aspects of cost, efficiency, quality, and safety, and analyze the complex factors and interdependence, a method combining DEMATEL(decision-making trial and evaluation laboratory) method and system dynamics is proposed to deconstruct and model the dependency relationship of various indices. First, 17 behavioral indices and performance evaluation indices of system dynamics model are determined. Second, DEMATEL method is used to quantitatively analyze the dependencies and transfer effects among indices, and the causal loop diagram(CLD) of the system dynamics model is constructed based on the comprehensive relationship matrix to reduce the subjectivity of the system dynamics model construction. Finally, based on CLD and the actual data of a tunnel in Yunnan, China, a multi-factor dynamic model of the construction digital twin benefit analysis system is constructed. The results show that when the mechanical cost is less than 7% of the total construction cost, the construction efficiency decreases significantly, and the sensor and mechanical input improve the performance approximately linearly, while there is a boundary effect when the information input exceeds 0.9% of the total cost.