Due to the unique structural mode and material property of a composite sandwich plate,related research such as fragment impact resistance of a composite mast is short of publication and urgent in this field.In this paper,the commonly accepted sandwich core board theory was modified.Damage caused by a fragment attack was simulated onto a sandwich plate model built with solid and shell elements.It was shown that shear failure and vast matrix cracking are the main reasons for outer coat damage,and tension failure and partial matrix cracking are the cause for inner coat damage.Additionally,according to complexities in actual sea battles,different work conditions of missile attacks were set.Ballistic limit values of different fragment sizes were also obtained,which provides references for enhancing the fragment impact resistance of a composite mast.