BACKGROUND:: Carboxyl group is introduced to hydrophobically modify polysaccharides, which could self-aggregate to nanoparticles with some surface charges, and it is beneficial to improving their stability and performing the good properties as a drug carrier. OBJECTIVE:: To synthesis cholesterol hydrophobically modified carboxyethyl pullulan (CHS-CEP), and to study their self-aggregated behavior in aqueous solution and characteristics of CHS-CEP nanoparticles. METHODS:: Acrylic acid and pullulan polysaccharides could form carboxyethyl pullulan (CEP) by additive reaction. Objective material could be obtained by catalyzing CEP and CSN. The synthesized material was characterized using proton magnetic resonance (H-NMR). The nanoparticles were prepared by dialysis to characterize the morphology, size and zeta potential by transmission electron microscopy (TEM) and dynamic laser scattering (DLS). RESULTS AND COUCLUSION:: By H-NMR analysis, it showed that CHS-CEP was successfully synthesized and this material could self-aggregate to form nanoparticles with opalescence. The diameter of CHS-CEP nanoparticles was about 148.6 nm and their zeta potential was-19.9 mV. They could act as drug carrier due to many excellent properties such as a good dispersity in aqueous solution, even distribution and long-term stability.Tao XJ, Tang HB, Ling K, Wang Y, Zhang QQ. Synthesis of cholesterol-modified pullulan and its self-assembled behavior. Zhongguo Zuzhi Gongcheng Yanjiu yu Linchuang Kangfu. 2011;15(51): 9633-9636. [http://www.crter.cn http://en.zglckf.com]