Chitosan is a linier copolymer (1→4)–linked 2-acetamido-2-deoxy-β-D-glucan (GlcNAc) and 2-amino-2-deoxy-β-D-glucan (GlcN) units in varying compositions. It is considered to be non toxic, reactive and abundant biodegradable material. Because of the advantages of chitosan, it has received much attention for many diverse applications in biomedicine, pharmaceutics, cosmetic, biomaterial, agriculture, food processing, and waste water treatment. Because chitosan has high molecular weight and also strong intra and intermolecular hydrogen bonding, ozonation becomes alternatives to degrade chitosan into chitosan oligomers and glucosamine. In this study, chitosan was treated with ozonation process with different composition and temperature process. After ozonation, chitosan was characterized by viscosimetry to determine molecular weight and the oligomers was analyzed by HPLC to determine the dissolved product. High molecular weight of chitosan was also characterized by FTIR to analyzed whether there was changing in side group of product.