Abstract: A box cover for a portable airtight box, comprising an upper cover, a lower cover, a sliding plate, a reset spring, a pinching member, a lower cover plate, and a sealing ring, wherein the upper cover is fixedly connected to the lower cover, an accommodating space is formed between the upper cover and the lower cover, and the sliding plate is movably arranged within the accommodating space, wherein the reset spring is disposed between the sliding plate and the lower cover, wherein the sliding plate is capable of moving upward relative to the lower cover, wherein the pinching member is movably arranged on the upper cover, and the pinching member abuts against the sliding plate, wherein the lower cover plate is movably arranged at outer bottom of the lower cover, and the lower cover plate is fixedly connected with the sliding plate.