The steady state energy spectrum of Tavis-Cummings model without rotating wave approximation using displaced coherent state method was studied.And the influence of initial state and coupling strength to concurrence were numerically studied.Our result demonstrates that the ground state of the system is non-degenerate with an exchange-symmetry between two atoms.The entanglement between two atoms always keeps maximal when the initial state is set to anti-symmetric while the non-entangled initial state produce entanglement periodically due to the effect of non-rotating terms.The coupling strength between the cavity field and atoms play a critical role in the entanglement dynamics.