The invention relates to a bottle plug comprising a plug body mainly made from a transmutable material and a cover body, wherein one end of the plug body is equipped with an annular convex part; the cover body is equipped with a top and an annular wall extending downwards from the bottom surface of the top, an ancillary wall is additionally extended in the annular wall, a combining groove is formed between the ancillary wall and the annular wall, a plurality of raised lines are equipped on the wall surface of the annular wall and the ancillary wall of the combining groove formed by the cover body, and the combining groove and the annular convex part of the plug body are tightly implanted and combined.