Abstract: Three dimensional large amplitude liquid sloshing in acyliindrical open tank under pitching excitation is studied in this paper.Firstly, the kinematics of the ALE description is introduced and the fluiddynamics equations are revised in the ALE form. The numerical discretedequations of fractional steps finite element method are developed byGalerkin weighted residual method. Lastly, the numerical simulation of largeamplitude sloshing of the liquid in cylindrical tank is carried out. Thecomputed water elevation history, the computed sloshing force history, thecomputed sloshing moment history and the computed free surface in differenttime are obtained. Numerical results are also analyzed in this paper.