We have studied the interaction between a cascacle three-level atom and the cavity field filled with Kerr medium by C-RWA. The influence of Kerr effect and virtual photon field on the photon anti-bunching is discussed. The results show that the quantum noise appears under C-RWA; the increase of x and ω or the decrease of g leads to the decrease of absorbance of atom and the reduction of photon antibunching;especially,the interaction is influenced obviouslly by g.