To invest thermosensitive, and biodegradable characters on polymeric amphiphiles, the poly(N-isopropylacrylamide)-b-poly(ε-caprolactone) block copolymers (PNPCL) with different PCL block length were synthesized by ring opening polymerization of ε-caprolactone and polymeric nanoparticles using these block copolymers were prepared by solvent evaporation. Then, Physicochemical characteristics of these nanoparticles were investigated by 1H NMR, DLS, FEG SEM and fluorescence spectroscopy. And, the thermosensitive nanoparticles were introduced into drug delivery systems using hydrophobic model drug of clonazepam (CNZ). We found that the PNPCL block copolymer formed nanoparticles and the characteristics of the nanoparticles were closely related to the hydrophobic/hydrophilic balance resulting from different PCL block lengths. ALso, we confirmed that PNP of thermosensitive micelle became hydrophobic and forms hydro-gel layer on surface of polymeric micelles above the LCST and this layer played a high potential for sustained release of drug due to hydro-gel layer on surface of micelles.