Abstract: Based on two kinds of biowastes (penicillin mycelia waste, PMW; herbal tea waste, HTW), the difference of biowastes derived from various sources and their fuel characteristics and combustion behavior after hydrothermal upgrading were investigated with the assistance of XPS, TGA and FTIR analyses. The results show that HTW mainly contains lignocelluloses, while PMW mostly consists of protein and polysaccharides. Although the specific conversion paths of various components are slightly different during hydrothermal process, both the higher heating values (HHV) of biowastes are improved (HTW:from 19.4 to 26.2 MJ/kg; PMW:from 19.1 to 29.3 MJ/kg); meanwhile, the coalification degree of biowastes increases with the growing temperature, even reaching the degree of bituminite at 300℃. In addition, the variation in carbon content and structure reflects that the reaction of devolatilization and aromatization during hydrothermal process can improve not only the fuel characteristics but also the combustion behavior.