In this experimental study,YAG:Nd laser beam was applied directly on the cock’s comb to evaluate its effect on vascular tissue.The YAG:Nd laser used had a wavelength of 1.06 μm and an output power of 25 watts,It’s spot size was constant at 2.5 mm.Biopsies were taken at an interval of 30 minutes after irradiation. Histopathologic study of cock’s comb wounds were carried out by common and electron microscope,which showed that the tissue impairment produced by YAG:Nd laser was similar to that of thermal burns,varying from superficial 2°to deep 2°～3°,depending upon the exposure duration to laser beam.In addition,the histologic study showed that YAG:Nd laser impaired the tissue with a three dimentional effect.