A novel diblock copolymer with a polyrotaxane block alpha-cyclodextrins-poly (epsilon-caprolactone)-b-poly{2,5-bis[(4-methoxypheny)oxycabony]-styrene } (alpha-CD-PCL-b-PMPCS) was successfully synthesized by combining ring-opening polymerization (ROP) and atom transfer radical polymerization (ATRP). The diblock copolymer was confirmed by H-1 NMR, GPC and solid-state C-13 CP/MAS NMR spectroscopic analysis. Its phase structures and phase transitions were investigated by thermogravimetric analyses and wide-angle X-ray diffraction (WAXD). WAXD and solid-state C-13 CP/MAS NMR spectroscopic study confirmed that inclusion complexes domains of the polyrotaxanes assumed a channel-type structure.