In this paper, we study the entropy properties of the field interacting with a Ξ type three-level atom, derive the calculating formula of the field(atomic)ent ropy, and discuss the influence of the initial atomic state and the one-photon d etuning on the field(atomic)entropy. With the help of Q function of the field(qu asiprobability distribution), the statistical properties of the field states are discussed. It is shown that the field is in the Schrodinger-Cat state at t=12TR when the atom is initially in the middle-level.