The time evolution of two coupling two-level atoms entanglement in a single-mode vacuum field is explored. The two-level atoms' reducible density matrix is obtained. The entangle ment between two two-level atoms is investigated by virtue of concurrence. The influences of the atomic dipole-dipole interaction on the entanglement of the two atoms are discussed. It is shown that the atomic dipole-dipole interaction leads to the decrease of the degrees of the entanglement and the increase of its time evolution period. In order to prepare entangled state, the influence of the atomic dipole-dipole interaction should be reduced.