The principle of measuring electron emission threshold of surface area metal electrode is presented. The measurement system of electron emission thresholds of two electrodes is developed. The electron emission characteristics of materials with different roughness degrees or Cr2O3 coating-deposit 40 um are measured in “Chenguang” accelerator. The results show that polishing can suppress electron emission. The higher the roughness degree of material, the lower the electron emission threshold is. Material coated with Cr2O3 has higher electron emission threshold than polished material.