In this research, environmental-responsive nanoparticles of chitosan-graft-poly(N-isopropylacrylamide) copolymers (CS-g-PNIPAAm) were prepared by the self-assembly method. The copolymer was first synthesized through polymerization of NIPAAm monomer in the presence of CS in an aqueous solution using cerium ammonium nitrate as the initiator. Then, the CS-g-PNIPAAm solution was diluted by deionized water and heated to a proper temperature for CS-g-PNIPAAm to undergo self-assembly. Micelles of CS-g-PNIPAAm were formed, and glutaraldehyde was added to reinforce the micelle structure to form nanoparticles. TEM images showed that a porous or hollow structure of nanoparticles was developed. The synthesized nanoparticles carried positive charges on the surface and their mean diameter could be manipulated by changing the temperature of environment. These nanoparticles with environmentally sensitive properties are expected to be utilized in hydrophilic drug delivery system.