Three different surface states of pure copper, pure tungsten and W70Cu30 alloy were obtained by machinery grinding, electrolytic polishing as well as mechanical polishing. By using dedicated device to simulate arc ablation process of the electrical contact materials, the arc-erosion resistance of these three materials were tested and the surface morphologies of first arc breakdown were investigated by SEM. The results show that the minimum roughness of 0.044μm for W70Cu30 alloy is obtained by mechanical polishing, followed by electrolytic polishing, and the maximum roughess is through machinery grinding. With the decrease of surface roughness, the breakdown field strength of the W70Cu30 alloy increases, the ablation region tends to be regular, the amount of ablation products increase and the ablation hole becomes more concentration. The same phenomenon also appears in pure tungsten and pure copper. In this experiment, the best arc-erosion resistance of materials is under the condition of surface roughness in 0.2−0.3μm.%将纯W、纯Cu和W70Cu30合金分别进行机械磨光、电解抛光和机械抛光后获得3种不同的表面状态，在专有设备上模拟电触头材料的电弧烧蚀过程，通过扫描电子显微镜观察首击穿烧蚀形貌。结果表明：通过机械抛光获得的表面粗糙度最小，对于W70Cu30合金可达到0.044μm，电解抛光次之，机械磨光最大；随表面粗糙度降低，W70Cu30合金的击穿场强逐渐增大，烧蚀区域趋于规整化，烧蚀产物增加，烧蚀坑的分布更加集中，纯W、纯Cu也表现出相同的现象；在本实验条件下材料表面粗糙度在0.2～0.3μm时，其抗电弧烧蚀性能最好。
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