A ring seal device for a trocar and a trocar. A rotary structure having a large upper end, a small middle part, and a large lower end is formed between guiding blocks (11) of a guiding mechanism (1). A positioning groove (10) is disposed at the wasp waist of the guiding blocks (11). The bottom of a seal ring (3) is embedded in the positioning groove (10) to surround the guiding blocks (11) from the outside to the inside. When a surgical instrument is inserted, the seal ring (3) pressed in the positioning groove (10) extends out of the gap between the guiding blocks (11) to surround the surgical instrument, thereby achieving sealing. The seal device reduces the contact area between the seal ring (3) and the surgical instrument as much as possible, has a guiding function when the surgical instrument enters or exits, and is applicable to insertion and exit of surgical instruments of various shapes. Furthermore, a "soft-hard" friction region between the seal ring (3) and the surgical instrument is converted into a "hard-hard" friction region between a plastic guiding surface of the guiding block (11) and an outer metal sheath of the surgical instrument to a greatest degree, thereby greatly reducing motion resistance faced by the surgical instrument in the seal device and the trocar. Meanwhile, the seal device and the trocar are applicable to a surgical instrument of any diameter between 5 mm and 12 mm, have an excellent seal effect, and incur low motion resistance.La présente invention concerne un dispositif de bague détanchéité pour trocart, et un trocart. Une structure rotative dotée dune large extrémité supérieure, dune petite partie intermédiaire, et dune large extrémité inférieure est formée entre les blocs de guidage (11) dun mécanisme de guidage (1). Une rainure de positionnement (10) se trouve sur la taille de guêpe des blocs de guidage (11). La partie inférieure dune bague détanchéité (3) est intégrée dans la rainure de positionnement (10) pour entourer les blo
