The entanglement property of two identical atoms, initially entangled in Bell states, coupled to a single-mode cavity is considered.Based on the reduced non-perturbative quantum master equation method, the entanglement evolution of the two atoms with decay is investigated beyond the conventional rotating-wave approximation.We shown that the counter-rotating wave terms, usually neglected, have great influence on the disentanglement behavior, of the system.The phenomenon of entanglement sudden death and entanglement sudden birth will occur.In addition, we show the entanglement can be strengthened by introducing the dipole-dipole interaction of the two atoms.