The entanglement properties of an atom interacting with Glauber-Lachs state in multiphoton Jaynes-Cummings model are studied by means of full quantum theory. The influences of the mean number of coherent photons, the mean number of thermal photons, the number of transition photons and the atomic initial state on the entanglement properties of the system are discussed. Results indicate that the entanglement is a non-monotonic function of the mean number of coherent photons and the mean number of thermal photons. With the increasing of the number of transition photons, the oscillation frequency of the entanglement degree of the system increases obviously and the average entanglement degree of the system decreases. And the atomic initial state affects the entanglement degree of the system obviously. Although the mixedness degree of atomic initial state tend to the ground state and to the excited state are identical, the effects on average entanglement of the system are different. The higher the degree of initial mixedness of the atom is, the more obvious the influence on entanglement degree of the system by the number of transition photons will be.