Biomass based raw materials can be converted into the more valued energy forms using biochemical methods such as ethanol fermentation, methane fermentation and the thermochemical methods such as direct combustion, pyrolysis, gasification, liquefaction. The bio-oil obtained from the biomass has many advantages than traditional use. Firstly, it has features such as high energy density, easy storage and easy transportation. Bio-oil can be used as a fuel in engines, turbines and burning units directly. Besides, it can be converted into products in higher quality and volume via catalytic cracking, hydrodexygenation, emulsification, and steam reforming [1,2]. Many organic solvents such as acetone, ethanol, methanol, isopropanol are used in the supercritical liquefaction processes. When we think about the cost and effects of the organic solvent on nature, it will be understood better that it is necessary to find solvent that are more sensitive against nature. Here, water must have an important place because of its features. Most important solvent of the world water is named as "universal solvent" because none of the liquids can dissolve the materials as much as done by water. Water is found much at the nature and cost of it is very few when compared with the other solvent. Hydrothermal liquefaction, a thermochemical conversion process is an effective method used for converting biomass into the liquid products. General reaction conditions for hydrothermal liquefaction process are the 250-374 degrees C temperature range and 4 - 22 Mpa pressure values range, besides, the temperature values can be higher according to the product that is expected to be obtained [3,4]. In this study, xanthium strumarium plant stems have been used as biomass source. The experiments have been carried out using a cylindrical reactor (75 mL) at the temperatures of 300 degrees C. The produced liquids at characterized by elemental analysis, GC-MS and FT-IR. According to the analysis, different types of compounds were identified by GC-MS.