The entanglement dynamics of two partially entangled two-level atoms interacting with a single mode vacuum field is investigated. The entanglement dynamics between two partially entangled two-level atoms and the vacuum field is explored by using the quantum reduced entropy,and that between two two-level atoms is studied by using the quantum relative entropy. The influences of the atomic dipole-dipole interaction intensity on the entanglement dynamics of the system are also discussed. The results show that the system exhibits periodic entanglement dynamics,and the magnitude and the period of entanglement depend on the atomic dipole-dipole interaction. The atom-field maximal entanglement state and atom-atom maximal entanglement state can be preparated by selecting appropriate system parameters and the interaction time.