The Sodium-sodium heat exchanger of the sodium cooled fast reactor is a vertical shell and tube heat exchanger, with the tube bundle area immersed in the sodium pool of the first loop. The radioactive sodium in the main cooling system of the first loop passes through the shell side, while the non radioactive sodium in the main cooling system of the second loop flows in the opposite direction from the tube side. When liquid sodium in the sodium pool laterally flushes the tube bundle, the heat exchange tubes may experience flow induced vibration phenomena such as amplitude surge, tube wall wear and thinning, flow induced instability, and even damage to the heat exchange tubes due to vortex shedding or turbulent shaking. The sodium- sodium heat exchanger heat exchange tube of a sodium cooled fast reactor serves as the boundary between the radioactive and non radioactive sodium sides of the sodium pool in the primary loop of the reactor. It plays a critical role in transferring the heat from the pool to the secondary loop, and its integrity and reliability are crucial for the safe operation of the reactor. Therefore, flow induced vibration analysis of the sodium-sodium heat exchanger heat exchange tube area is necessary. The tube bundle structure of the sodium sodium heat exchanger in a sodium cooled fast reactor is different from that of a conventional shell and tube heat exchanger. The tube bundle structure adopts a spatial bent tube structure, and the applicability of the existing design standard flow induced vibration analysis method for this structure still needs to be evaluated. This article uses numerical simulation analysis methods, combined with existing mathematical models in design standards, to derive a set of flow induced vibration analysis methods suitable for the space bent tube bundle structure of sodium sodium heat exchangers. Based on experimental data, this flow induced vibration analysis method is improved and revised.