Abstract: In this study,the influence of feedwater pH value（3-11） on hydrothermal carbonization（HTC）of microcrystalline cellulose（MC）at 220 ℃,4 h is studied. Sodium hydroxide, sodium bicarbonate and citric acid are used to prepare solutions of different pH values,respectively. Elemental and scanning electron microscopy（SEM）analyses are used to investigate the influences of the pH values of the solutions from 3 to 11 on the physical,chemical,thermal and structural characteristics of hydro-chars. The van Krevelen diagram is also used to analyze the influences of the pH values of the solutions on the hydrothermal carbonization process. Results show that the mass yield and carbon fixed rate（FC）decrease with increased acidity. Hydro-char yield and FC are only 35.5% and 41.82%under the pH value of 3,and the hydro-char possesses the best aromaticity. Whereas at pH value of 11,the hydro-char yield and FC reach as high as 46.5% and 48.91%,respectively and the hydro-char has the best hydrophilic. Dehydration is the main reaction during the HTC process. SEM images show that the microsphere size of HCA（hydro-chars from acidic condition）decreases with increased acidity while HCB（hydro-chars from basic condition）have uniform microsphere size and good sphericity.