A preservation container cover includes a flexible film to contact with the rim of the container, an upper sealing ring, and a lower sealing ring affixing a periphery portion of the flexible film. The upper sealing ring has a ring slot extending along the periphery portion of the flexible film. The lower sealing ring comprises a ring plug along the periphery portion of the flexible film. The ring slot and the ring plug form a clamp structure to affix the flexible film. The present invention is convenient to use, adaptable to various containers of different types and sizes, and won't cause waste of natural resources and environment problems.