Abstract: Arbitrary Lagrangrian-Eulerian(ALE) method has many advantages,such as flexible meshing,high computational precision and wide applicability.It is especially applicable to the fluid-structure interaction problem in hypothetical core disruptive accident(HCDA) of liquid-metal fast breeder reactor.In HCDA the free surface of liquid sodium deforms severely.In present paper,the FEM equations for HCDA analysis are derived based on the ALE formulation.A relevant FEM code is developed and used to analyze the fluid-structure interaction problem of HCDA.The CONT standard examination,which is usually used to check the computational programs for LMFBR,is performed and the numerical results agree well with the available results in the open literature.