Polyrotaxanes (PRs), in which alpha-cyclodextrins (alpha-CDs) were threaded onto poly(ethylene Glycol) (PEG) chains capped with beta-cyclodextrins (beta-CDs), were prepared by click chemistry via a one-pot strategy in water at room temperature with high yield, tip to 320 mg/100 mg PEG axis. The terminal beta-CD cavity could be recognized by phenolphthalein and utilized to form a supramolecular block copolymer with alternate rod and coil segments via the formation of a host-guest inclusion complex with diadamantyl-terminated PEG. The prepared PR could further work as a novel template for the in situ deposition of platinum (Pt) nanoparticles (NPs) to fabricate metallic nanowires. TEM and SEM observations showed that the resulting polycrystalline nanowires with length of 50-200 nm and diameter of ca. 12 nm were composed of close-packed uniform Pt Nil's with diameter of ca. 2.5 nm. The catalytic activity of the Pt nanowires was demonstrated by the reduction of 4-nitrophenol. The fascinating beta-CD-capped PR is promising in a wide variety of fields such as supramolecular chemistry and bionanotechnology due to its facile and salable availability and biocompatibility.