The oven mouth of coke oven is equipped with an oven door which is freely removable. If the oven door is untightly sealed, the gas can leak from the coke oven, therefore its sealing measure is very important. The present invention is that a sealing band made from metal thin sheet covers the oven mouth, and a heat-insulating air-cooling space is provided between the sealing band and the oven door body, and at the same time the sealing band can be slided up and down between the oven door body and brick bracket so as to absorb the difference in thermal expansion and contraction. Besides, the oven door knife-edge which is installed around the sealing band always is tightly pressed against the door frame by use of a plunger so as to ensure its sealing performance. A water-proof cover is installed on the spindle of said plunger so as to prevent water from entering into its interior when washing, therefore the present invention can provide a coke oven door whose sealing capability is good.