The invention relates to a single-degree-of-freedom double-mode infinite turning mechanism. These mechanisms all include first to third scissor branch chains (1, 2, 3), and the first scissor branch chain (1) and the second scissor branch chain (2) pass through the first and second right connecting rods. (1‑3, 1‑4), the third and fourth left connecting rods (2‑1, 2‑2) realize the rotational connection; the second scissor branch chain (2) and the third scissor branch chain (3) Through the third and fourth right connecting rods (2-3, 2-4), the fifth and sixth left connecting rods (3-1, 3-2) to realize the rotational connection; the third scissors branch chain (3) and The first scissors branch chain (1) realizes rotational connection by the fifth and sixth right connecting rods (3-3, 3-4), the first and the second left connecting rods (1-1, 1-2); The above connection, the whole mechanism forms a closed loop. This type of single-degree-of-freedom mechanism has a dual motion mode of columnar scaling and infinite flipping, which can be contracted into a bundle or expanded into a polygonal loop; at the same time, by changing the first to third scissor branches (1, 2, 3) The number of scissor elements, which can adjust the scaling ratio of the polygonal loop shape and the mechanism.