Applying the method of coherent-state orthogonalization expansion, the influnences of dipole-dipole interaction and the coupling strength on the entanglement between two atoms of the Tavis-Cummings model without rotating wave approximation(without-RWA) are studied. Compared with the rotating wave approximation(RWA), it is found that the entanglement of the without-RWA agree with that of RWA when the coupling strength is weak. In the strong coupling regime, the sudden death phenomena occurs. The results also show that the stronger the atom-field coupling strength is, the longer the state stays in the disentangled separable state, which means that the length of the time interval for the distanglement depends on the atom-field coupling strength. When the dipole-dipole interacton is taken into account, the entanglement of the two atoms will be enhanced with the increace of dipole-dipole interaction.