The evolution properties of quantum entanglement in a system of multimode coherent field interacting with two identical two-level atoms through degenerating multi-photon process are investigated using the Von Neumann quantum reduced entropy theory, and the analytical expression of quantum entanglement and the numerical calculation results for two-mode field interacting with the atoms are obtained. The results show that: the quantum entanglement will strengthen with the enhancement of the photon degeneracy; the periodicity of the quantum entanglement will become more and more apparent with the increasing of the average photon number; when the field and the atoms are far from resonance, the quantum entanglement will decrease with the increase of the frequency detuning; when the frequency detuning is large enough, the field and the atoms are nearly always in entangled states. These results are useful for the preparation of the entangled states or pure states and for quantum information in optics systems.