In this work, the catalytic conversion of natural polymer chitosan to 5-HMF under low temperature hydrothermal condition was investigated. The highest 5-HMF yield of 12.1 wt% was obtained under the following conditions: 174 degrees C reaction temperature, 2.2 % catalyst amount, and 36.9 min reaction time. In the effect of combined severity, the 5-HMF production linearly increased to the combined severity factor of 3.07. By the way, higher combined severity factor can cause the over-degradation of 5-HMF. From this result, chitosan showed significant potential as a feedstock for the production of platform chemicals such as 5-HMF.