A system is provided for creating a modified analytical model from an existing analytical model and CAD data (geometric model data) of the modified model to reduce the workload in creating geometric and analytical models. The system includes means for reading a geometric model and an analytical model which are to be modified; means for storing correlation data showing relations between geometric elements of the object geometric model and nodes of the object analytical model; means for modifying the object analytical model to create a modified analytical model; and means for extracting geometric elements of the object geometric model which do not include the nodes in the modified object analytical model related to the object geometric model's geometric elements extracted from the correlation data and performing geometric fitting so as to fit the extracted geometric elements to the nodes to create a modified object geometric model from the modified analytical model.