The entanglement dynamics of two atoms initially in an entangled state system interacting with a bimodal field is investigated by making use of the concurrence and linear entropy.The effect of the initial entanglement degree of two atoms and the cavity field on the time evolution of concurrence is analyzed.The results show that the phenomenon of sudden death of the entanglement between two atoms occurs.The length of the death time interval is independent of the initial entanglement degree of two atoms.However,the death time depends on the initial entanglement degree of the cavity field.The atom and the field are entangled during all the evolution process.