The invention discloses a method for preparing fuel oil by hydrothermally liquefying kitchen waste, which can realize fast and efficiency resource utilization of the kitchen waste. After the kitchen waste is collected, inorganic impurity in the kitchen waste is separated, and the residue is used as raw materials; the separated raw materials are subjected to centrifuging and standing processing, grease on the upper layer is separated as biodiesel or industrial grease raw materials, massive residue food in the lower layer and swill turbid liquid are fed into a hydrothermal reaction kettle, a temperature in the reaction kettle is controlled within 290-350 DEG C, a self pressure range is 8-15MPa, stirring and standing under a hydrothermal condition for 20-60min are performed, a relief valve is opened, and discharged high temperature steam preheats charged materials and is recycled. After pressure relief, an organic solvent (mixed alkanes) is added to extract product oil adhered to the bottom and wall surface of the reaction kettle. The method for preparing fuel oil by hydrothermally liquefying kitchen waste can realize resource utilization of the high water content kitchen waste, and organic waste with an extremely low heat value is subjected to hydrothermal liquefying to prepare the fuel oil with a high heat value and high additional value.