Abstract: As the key technology of digitalization and intelligentization of manufacturing, the development of digital twins (DT) technology has put forward new requirements for new simulation methods. Real-time cyber-physics fusion is a key aspect of digital twins. Taking friction stir welding (FSW) as example, a novel iterative cyber-physical fusion algorithm to realize the real-time calculation of the 3D temperature field is established. The viability of real-time simulation of 3D temperature field in FSW is demonstrated. The result shows that the proposed algorithm has high reliability, and the average error of the temperature calculated based on the proposed algorithm relative to the measured temperature in experiment is within 5 ℃. It is interesting to mention that, if a time step of 1.5 s or 2.0 s is utilized, the calculation time will be shorter than the physical process of welding. This enables numerical simulation and FSW physical processes to be synchronized with a second-level temporal precision. It is proved that integrating real-time sensor data into numerical simulation model synchronizing with physical process can be a practical method of realizing digital twin modeling of welding process.