Considering a model containing two two-level atoms and a single-mode cavity, the effects of the time-dependent atom-field coupling on entanglement between the two atoms were researched when the two atoms are initially in an entangled state. The results show that, the time of initial entanglement preservation is very sensitive to the linear modulation of the atom-field coupling. Compared to the case of the constant coupling model, when the atom-field couplings change smoothly, the disappearance of the initial entanglement is delayed due to the linear modulation. However, the disappearance of the initial entanglement can be hastened for the sudden jump in the coupling.