Concentric diffraction rings with bright center in the far field and dark center in the near field of the probe beam were experimentally observed when a strong pump laser beam (526nm) and a weak probe laser beam (632.8nm) cross under the no nlinear medium film (Polypyrrylarylenemethine/polyvinyl film).Based on Fresnel-K irchhoff diffraction integral equation,this phenomenon can be explained by the d iffraction effect of the probe beam from the laser-induced phase-hole in the non linear medium caused by the pump beam.The numeric calculations give good agreeme nt with the experimental results.