With the continuous development of the technology and informatization, the current research and application of the technology of the digital twin has become a hot spot. The technology of the digital twin is applied to the optical-mechanical system design, the optical-mechanical manufacturing, the optical-mechanical installation and calibration, as well as the inspection over the whole process and the whole life cycle. The objective of this paper is to study the construction of the digital twin in the crucial links of the installation and calibration process over the whole process of the optical-mechanical system, as well as the modeling and simulation of the digital twin in the optical-mechanical installation and calibration process, including the ideal model simulation, the optical-mechanical part-level simulation, the optical-mechanical thermal coupling simulation, the total integration simulation, as well as the prediction of the use effect of the optical-mechanical system. In the past, the ex post data were collected in order to feed back for the model design and the process, so as to improve the accuracy of the simulation. Accordingly, the actual measured data of the optical-mechanical part entity are substituted into the model. Moreover, the results of the simulation integration are used to correct the technical scheme of the process. Furthermore, the physical entity data generated during the execution of the correction scheme are transmitted to the simulation model once again, so as to achieve the dynamic data interactive application of the optical-mechanical system in the physical entity and the virtual model. Thus, the dynamic system is formed. In the end, the data exchange, sharing as well as the mutual mapping between the physical entity and the virtual entity during the installation and calibration of the optical-mechanical system can be realized. In conclusion, the provision of the real-time data, the analysis and optimization of the installation and calibration process, as well as the decision making of the implementation plan in the aspect of the installation and calibration application of the optical-mechanical system, which provide an effective way for the process design of the installation and calibration of the optical-mechanical system as well as the digital improvement of the installation and calibration technology. © 2023 SPIE.