Abstract: Abstract: Rapid industrialization and urbanization have brought a severe problem of energy shortage and environmental pollution into our life. As the fourth-largest energy, Nowadays, Lignocellulosic biomass is increasingly regarded as an eco-friendly renewable feedstock for producing various bio-based products. Recently, hydrothermal carbonization (HTC) as a hot topic has attracted a great deal of attention because the process requirements of HTC are comparably low and are able to treat wet feedstock without an energy extensive drying process. But so far, some literatures have focused on the morphology, chemical structure and adsorption capacity of hydrochar, etc. Only few reports have provided a detailed description on the kinetic analysis of hydrochar. Pyrolysis is considered as the first step of the process of gasification, liquefaction, carbonization, and combustion. On the other side, the knowledge of the pyrolysis kinetics is fundament for predicting the pyrolysis behavior of materials and the design of the suitable reactor. In this study, pine sawdust was provided by a factory in Anhui province in 2015. The hydrochar was hydrothermally obtained from 5 g of sawdust immersed in 40 mL of distilled water in the stainless steel autoclave keeping temperature at 200 ℃ for 6 h, then as-prepared hydrochar was dried in an oven at 105℃ for 24 h. Pyrolysis characteristics and organic structure of both pine sawdust and hydrochar were investigated via thermogravimetric analysis and Fourier transformation infrared spectrometer, respectively. Different heating rates (10, 20, 30 ℃/min) were chosen to study the influence of pyrolysis process. Meanwhile, the distributed activation energy model (DAEM) was used to study the pyrolysis kinetics by means of the relation between conversion rate and activation energy. The results indicated that : 1) Compared with pine sawdust organic structure of hydrochar treated by hydrothermal carbonization process was changed, and the organic function groups of pine sawdust and hydrochar decreased in the different ways with the increase of pyrolysis temperature, but the organic function groups of hydrochar decreased faster than pine sawdust's when the temperature was over 200 ℃; 2) Thermogravimetric curves showed that hydrochar needed higher temperature and led to the faster loss weight rates than pine sawdust during the pyrolysis process, but the trend of thermogravimetric curves of both products changing with heating rates was same; 3) The values of pyrolysis activation energies of hydrochar and pine sawdust were different ranging within 99.33-252.72 and 63.77-211.68 kJ/mol, respectively. But the trends of the pyrolysis activation energies of hydrochar and pine sawdust were very similar with the increment of conversion rate. In summary, hydrothermal treatment process destroyed organic functional groups and lowered volatile content of pine sawdust, resulting in the changes of pyrolysis characteristics. Specifically, the whole pyrolysis process shifted to higher temperature, the reaction rate was accelerated and the main pyrolysis process occurred in a narrower temperature range shortening the pyrolysis time. Activation energy also was influenced due to the hydrothermal process, leading the reduction of the values at the dominating stage of volatile loss, however, the increase of the values at the initial and final stage of volatile loss. This study provides reference for pyrolysis and mechanism of hydrochar production.