Disclosed herein are clathrate hydrate inhibitors and the method of inhibiting the formation, agglomeration, and deposition of clathrate hydrate using the inhibitors. The clathrate hydrate inhibitor comprises a macromolecular compound in which 3-15 membered ring pendant is connected to the polymer main chain via a specific spacer group such as homo- or co-polymer of (meth)acryloyl pyrrolidine, pyrrolidinocarbonylethyl (meth)acrylate, 2-oxo-pyrrolidino-ethyl (meth)acrylate, glyoxyloyl pyrrolidine, pyrrolidinocarbonyl aspartate.