In view of the large amount of toxic gases and solid particles produced during the spraying operation in the automatic spraying workshop of large segmented hull,it is difficult to monitor the real-time spraying,and the problem of the poor film-forming quality caused by the mismatch between the actual spraying data and the performance of the process system,the intelligent monitoring method based on digital twin technology was proposed.The system architecture of digital twin 5D model and twin model were established,the model data-driven technology were used,and the new digital twin modeling method for spraying film thickness was emphatically proposed.Through experiments and simulation comparison,the digital twin system can highly restore the spraying film thickness and its uniformity.Combined with the characteristics of cyclic iteration of spraying process,through accumulating and processing field data,the system can iteratively optimize the spraying process parameters before,during and after processing,so as to improve the spraying efficiency and spraying quality.