The careful synthesis of drug carrier is important because it has the property of biodegradable and bio-compatible, and the role of easy and effective release in drug delivery system (DDS). Chitosan oligosaccharide (COS) which produced by the hydrolysis and enzyme degradation of chitin from the crustacean has been recently studied as a medical substrate for anti-cancer agents of DDS. Gold nanoparticles (GNPs) have been used antioxidant and biomaterial for cancer therapy because GNPs have photochemical and light sensitive properties to be applicable to medicinal system. COS-GNPs nano-composite with COS of various cross-linking agent concentration and GNPs of various reducing agent concentration by using interactive force between COS and gold nanaoparticles was prepared in this study. The composition and morphology was confirmed by Transmission electron microscope (TEM), Atomic Force Microscopy (AFM), Ultraviolet-visible spectroscopy, and it was applied to cancer therapy.