To analyze the dynamic characteristics of the gravity support system of ITER, according to the characteristics of cyclic symmetry of the gravity support system of ITER, the 3-D FEM model with 20 degree sector of the gravity support system was built by using ANSYS. Meantime, a mesh dividing method, which has high precision and an acceptable calculating scale, was used. After the mesh of the model had been divided, the contact elements were defined on the interfaces between flanges. The modal analysis of the gravity support system was made and the first ten natural frequencies and vibration modes of the gravity support system were solved by using Block Lanczos method. The results of the modal analysis can be used to the design and improvement of the gravity support system of ITER.
