A novel amphiphilic polymer having a hyperbranched polysaccharide core, 2, was synthesized by carbamation of hyperbranched polysaccharide (1) using N-carbonyl L-leucine ethyl ester in pyridine at 100°C . The carbamation reaction homogeneously proceeded to afford a light brown polymer (2), which was soluble in methanol, acetone, and chloroform but insoluble in water. The amphiphilic polymer 2 possessed an encapsulation ability of water-soluble molecules (such as rose bengal, thymol blue, and alizarin yellow) in a chloroform phase. Rose bengal (RB) encapsulated in polymer 2 slowly released into water at a neutral pH condition, while the release rate was extremely accelerated in a basic condition.