New amphiphilic thermosensitive poly(N-vinylcaprolactam)/poly(D,L-lactide) (PNVCL-b-PLA) block copolymers were synthesized by combining ring-opening polymerization of D, L-lactide (LA), free radical polymerization of N-vinylcaprolactam, and subsequent click chemistry. Their structures were characterized by IR, H-1 NMR, C-13 NMR, and GPC measurements. The fluorescence technique showed that these copolymers could self-assemble into nano-micelles in water and the CMC values of the copolymer solutions reduced with the increasing of the proportion of hydrophobic segments. Dynamic light scattering demonstrated that the sizes of micelles reduced with the increasing of the proportion of hydrophobic segments. Transmission electron microscopy images demonstrated that all micelles were spherical. On the other hand, the UV-vis measurement showed that these block copolymers exhibited a reproducible temperature-responsive behavior with a lower critical solution temperature that was tunable by the block composition and the concentration of the copolymers.