A series of amphiphilic and thermo-responsive block copolymers were synthesized by reductive amination between the aldehyde endgroup of hydrophilic HPMC and the amine group of monoamine, diamine, or triamine JEFFAMINE as hydrophobic block. The resulting diblock, triblock and three-armed copolymers with different hydrophilic/hydrophobic ratios and block lengths were characterized by NMR, FT-IR, DOSY-NMR and SEC. The cloud point (CP) of copolymers was determined by UV-visible spectrometer. Data show that both the geometrical structure and the molar mass of HPMC affect the CP of HPMC-JEF copolymers. The higher the hydrophilic/hydrophobic ratio, the higher the CP of copolymers which is lower than that of HPMC homopolymers. The self-assembly behavior of the copolymers was investigated from dynamic light scattering, transmission electron microscopy, and critical micelle concentration (CMC) measurements. Spherical nano-micelles are obtained by self-assembly of copolymers in aqueous solution, and the micelle size can be tailored by varying the block length of HPMC and the geometrical structure. Three-armed HPMC-JEF copolymers present lower CMC and smaller micelle size as compared to linear diblock and triblock ones. MTT assay evidenced the cytocompatibility of HPMC-JEF copolymers, indicating that they could be promising as drug carrier in drug delivery systems.