In this paper, some recent advances in our research on hydrothermal conversion of biomass into useful substances are presented. Here, we mainly focus on the production of acetic acid and lactic acid from carbohydrates including aldose, lignocellulosic biomass, and glycerin along with the discussion of some reaction mechanisms and the interaction between the main components of natural material, such as cellulose and lignin in lignocellulosic biomass. A large-scale continuous flow reactor system was also presented.