The dynamics of entanglement of two two-level atoms initially in excited state interacting with a Fock state field is examined by means of concurrence. The effects of photon number, atom-cavity detuning and manipulation of the atom on the time evolution of concurrence are investigated. The results show that the phenomenon of sudden birth of entanglement between two atoms occurs in the absence of the manipulation of the atom. Moreover, the threshold time for the creation of entanglement and the maximum of the entanglement can be controlled by the photon number and the atom-cavity detuning. The entanglement between two atoms can be created immediately as time develops in the presence of manipulation of the atom. The atom-atom entanglement can be manipulated by the application of the classical field.