The utilization of high molecular weight chitosan have been limited by insoluble in water. For these reasons, molecular weight of chitosan was degraded to apply in various biomedical field by potassium persulfate (KPS) as thermal initiator agent. The KPS was added to the chitosan solution and the mixture was reacted under nitrogen atmosphere at 60°C . The molecular weight of degraded chitosan was analyzed by gel permeation chromatograph (GPC). The results showed that degree of degradation of chitosan was depended on reaction time and quantity of KPS. In addition, characterization of degraded chitosan was analyzed by FT-IR, 1H-NMR, TGA and DSC. Therefore, degraded chitosan can apply to biomedical field. ^** This work was supported by National Research Foundation of Korea (NRF) grant funded by the Ministry of Science, ICT & Future Planning (No. NRF-2016H1D5A1910499).