To explore how the degree of cathode oxidation influences the ignites characteristics of ring He-Ne laser, photoelectric retarding potential method is used to investigate the variation of the work function with the cathode oxidation. As the cold cathode of discharge device, aluminum′s work function and the work function variation before and after oxidation are measured under the high vacuum conditions by Лукирский spherical photo electronic measure equipment and parallel electrodes optic-electronic & discharge device. The experimental results show that work function of aluminum cathode in the natural oxidation is 2.60±0.2 eV.The mass percent of oxygen on aluminum cathode surface is 3.2%.At different times of oxidation process, the work function of aluminum cathode decreases with the growth of the oxidation time. The reasons that work function measurements of aluminum cathode may be in 2.5～4.3 eV are explained. The conclusion from the experimental results is the oxidation time is longer, the smaller the work function of the material, the more conducive to the ignition of the ring He-Ne laser within a certain range. Cathode oxidation also affect the ignition voltage and the cathode potential drop of gas discharge process .So the choice of the optimal oxidation time ought to consider these two factors.