Under on-resonance condition and with a time-dependent atom-field coupling,we study the entropy properties of the field interacting with a V-type three-level atom,and discuss the effects of the atom-field coupling coefficient and the different initial field on the field(atom)entropy at length. The results show that the different statistical properties of the initial field will lead to the change of the field(atom)entropy. When the atom-field coupling coefficient changes slowly,the speed of atom entering the statistical state is slowed;When the atom-field coupling coefficient changes rapidly,the oscillating frequency of the evolution of entropy speed up.