Based on information regarding the excavation progress, support progress, and newly outcropped geology at the construction site of a large-scale underground cavern group, a three-dimensional numerical simulation model, which can be updated in real time and reflect the practical process of construction, was established. Using the techniques of uniform design and artificial neural networks and the mixed programming technique of C#. NET+Python, the secondary development of ABAQUS proceeded, and a method of real-time dynamic inversion of surrounding rock mechanical parameters was developed for a large-scale underground cavern group during the construction period. Using the Huangdeng Hydropower Station as an example, real-time dynamic inversion of surrounding rock mechanical parameters during the construction of a large-scale underground cavern group was conducted. The results show that the variations of calculated displacement and measured displacement of measuring points with construction time showed the same pattern of change in different construction periods and were in good agreement. The average error was only 5. 5% in the fifth construction period. This good inversion result verifies the rationality and maneuverability of this method.