The invention discloses a plastic bottle cap having a sealing structure and convenient rotation, including plastic cap body. The bottom side of the cap body is an opening, and the inner wall of the cap body near the bottom side opening of the cap body is annularly provided with a groove. The sealing ring is installed in the groove, one side of the sealing ring extends to the outside of the groove. The annular groove is opened around the inner ring of the bottle cap body. Two semi-circular rings are movably mounted in the annular groove, one end of the two semi-circular rings is rotatably connected by the first hinge, one end of the two semi-circular rings which far away from the first hinge is fixed with the first fixing block and the second fixing blocks respectively, The first fixing block and the second fixing block correspond to the setting. The present invention can quickly and conveniently open the sealing structure on the cap body, and the sealing structure is easy to reuse. At the same time, the cap body can be rotated quickly and conveniently to prevent the cap body from sliding when the cap body is rotated. The utility model has the advantages of simple structure and convenient use.