In order to illustrate the evolution process and working mechanism of the cerium–tungsten electrode of the high-power pulsed xenon lamp during operation, the cathode surface morphology of the high-power pulsed xenon lamp running for different times, the evolution of the valence state of cerium and its concentration–depth distribution have been studied using a metallurgical microscope, scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and other methods. The results show that a large number of cracks and ablation of different degrees appear on the working surface of the cerium–tungsten electrode; the degree and depth of the cracks and the ablation depend on the running times; and the crack and ablation are more serious with more working times. As the running time increases, the cerium on the cathode surface diffuses to the working surface of the cerium–tungsten electrode, with the content of cerium increased for a uniform distribution. Through the analysis of Ce3+/ Ce4+ ratio, it has found that the surface activity of the cerium–tungsten cathode running 6466 and 10083 times is in a better state; and the surface activity layer of the cerium–tungsten cathode running 14486 times is significantly reduced, and the electrode is approaching its service life.