The entanglement between the two atoms of two separate Jaynes-Commings models is investigated by means of the concurrence. We restrict our attention to two cases, the field frequency varying with time in the forms of sine and rectangle. When the field frequency varies with time in the form of sine, the period and the amplitude of the atom-atom concurrence will decrease as the amplitude of the sine frequency modulation increases. Not only the sine field frequency modulation but also the rectangular field frequency modulation can affect the interaction of the field with atom between resonance and off-resonance. The field frequency modulation can also affect the atom-atom entanglement. The suitable field frequency modulation is favorable for improving, enhancing and stabilizing the degree of the atom-atom entanglement. The suitable field frequency modulation can also prevent the atom-atom entanglement from entanglement sudden death and control it dynamically.