Abstract: The effect of Kovar alloy oxidized in simulated field atmosphere on its sealing with glass was studied in this article. After Kovar plates and pins were preoxidized in N₂ with 0℃, 10℃ and 20℃ dew points at 1000℃ for different times, Fe₃0₄ and Fe₂0₃ existed in the oxidation products on Kovar surface, and the quantity of Fe₂0₃ increased with increasing dew point and oxidation time. Then they were sealed with borosilicate glass insulator at 1030℃ for 20 rain. The results indicated that the type and quantity of oxidation products would directly influence the quality of glass-to-metal seals. With the increase of oxidation products, gas bubbles in the glass insulator were more serious, the climbing height of glass along the pins was higher, and corrosion of Kovar pins caused from the molten glass was transformed from uniform to the localized.