When a yellow pcntoxide vanadium sample is explored to a proper fluence excimer laser, its electric conductivity changes remarkably. So, it changes from an insulator to a semiconductor, besides its color changes too. The pentoxidc vanadium sample, before and after being acted, is analysed with the X-ray diffraction (XRD) , X-ray photoclectronic spectrum (XPS), and microscopy. It can be determined that the procedure takes place because the proper flucncc excimer laser illuminates the surface of the pentoxide vanadium sample, the temperature on the surface rises quicikly, and a thin layer of the illuminated area is molten and then resolidifies quickly, which leads to the chemical ratios change of the sample surface.