Gold nanoparticles (GNPs) are of unique and interesting materials being firstly reported 100 years ago. They are one of the most widely studied nanomaterials potential for disease cure. To improve the colloidal stability, biocompatibility, and hemocompatibility of GNPs, chitosan (CS), a naturally produced polysaccharide with excellent biocompatibility and biodegradation, has been modified to generate water-soluble derivatives and used as the stabilizing agent of GNPs. In the presence of these derivatives, GNPs are stabilized, functionalized, and assembled via electronic static and covalent bond interactions. Based on these works, GNPs with different dimensional, morphology, and crystal lattice are obtained, which can be further apply to a variety of applications in sensing, imaging, therapy, and catalysis.