A hair extension kit enables user's hair to be coupled with extended hairs, and includes a fastening ring formed in a hollow shape, each respective upper end of the extended hairs being attached to an inner peripheral surface of the fastening ring; a guiding loop having a portion thereof received in the fastening ring and a guiding and holding part formed at the lower end thereof, the guiding loop being removable from the fastening ring; and a drawing loop having a portion thereof received between an inner wall of the fastening ring and the corresponding part of the guiding loop and a drawing and holding part formed at the lower end thereof, the drawing loop being removable from the fastening ring. The hair extension kit can increase the coupling force between the user's hair and the extension-hair via the fastening ring.