A method for establishing a vacuum in a container includes the following steps. The container having an exhaust through hole defined therein is provided. A sealing cover including a connecting material located on the periphery of the sealing cover is provided. The sealing cover is spaced from the exhaust through hole for form at least gaps between the sealing cover and the exhaust through hole. A vacuum is established in the container. The connecting material is heated. The sealing cover covers the exhaust through hole and the connecting material is cooled. After that the container is packaged.