By means of the quantum theory,we investigate the system of two two-level atoms coupled to a single mode cavity in the vacuum state with the phase decoherence and calculate the entanglement time evolution between two atoms in the presence of phase decoherence. It is shown that the influences of the phase decoherence coeffident, the two-atom initial state and the dipole- dipole coupling intensity between two atoms on the entanglement degree of two atoms are revealed. The phase decoherence causes the fading of entanglement between two atoms,the entanglement will quickly become a constant with the increasing of the phase deeoherence coefficient; the constant value is affected by the two-atom initial state and the dipole- dipole coupling intensity. Meanwhile the two-atom quantum state will forever stay in the maximum entangled state when the initial state is proper even in the presence of phase decoherence.