Fidelity is an important concept in quantum optics and information optics, the study on fidelity is meaningful for the development of quantum teleportation and quantum calculation. The properties of the evolution of the fidelity and fidelity amplitude for degenerate Raman process in the presence of the Stark shift were investigated by means of quantum theory, the influence of the Stark shift parameter and average photon number on the fidelity were discussed. Results show that the less the Stark shift is, which will weaken the interaction between the field and atom, and the higher the fidelities of the three systems are. On the other hand, the more the initial photons are, which strengthen the interaction between the field and atom, and the lower the fidelities of the system and atom.