The two-photon transition for a two-level atom interacting with a single-mold electromagnetic field has been investigated. The initial coherent states with time-varying frequency are considered. The effects of the frequency modulation in sinusoidal form on the atomic population inversion and the squeezing properties of the atom and field are studied. The frequency change can lead the collapse-revival period of population inversion to increase, the maximum value of the revival to decrease, and the squeezing effects of the field and atom are weakened.