During the drilling process of horizontal wells, the uncertainty of the actual position of the wellbore and the vertical depth of the target point can result in the trajectory needing to be dynamically adjusted based on monitoring results during the actual drilling process. In the existing trajectory control methods, trajectory monitoring and trajectory dynamic optimization were designed as two relatively independent links, and the entire process was time-consuming and slow in response, which cannot meet the requirements of fast decision-making and precise control in the intelligent closed-loop control of wellbore trajectory in the next generation of intelligent drilling. Therefore, an intelligent monitoring and control digital twin system for horizontal wellbore trajectory was constructed, which utilizes the characteristics of virtual real interaction, real mapping, and zero-risk virtual verification of digital twins to establish a bidirectional connection between wellbore trajectory design, real-time monitoring, and autonomous control, achieving integrated intelligent closed-loop control of wellbore trajectory design, real-time monitoring, and autonomous control. And the operation mechanism and the key technical theories of intelligent monitoring and control of horizontal well trajectory in the digital twin system were elaborated from three aspects: construction, evolution, and update of the digital twin system. The rationality of the digital twin system has been demonstrated through case simulations, and the practicality of the system architecture has been demonstrated through the application of trajectory change trend monitoring and trajectory dynamic adjustment functions. This system can combine intelligent monitoring and control technology of horizontal wellbore trajectory with intelligent devices to achieve integrated intelligent closed-loop control of the entire cycle of horizontal wellbore trajectory, providing theoretical support for achieving intelligent drilling.