The invention relates to a waste lubricating oil pretreatment technique, belonging to pretreatment of waste lubricating oil before refinement. The invention aims to remove nonideal components (such as light hydrocarbons, moisture, gasoline, metal particles, carbon granules, dust, oil sludge, additives, residue asphalt, mechanical impurities and the like) in the waste oil to obtain the pretreated oil without impurities. The technique is characterized by comprising the following steps: 1) filtering the waste oil to remove large mechanical impurities; 2) adding 0.5-3.0% of pretreating agent, and stirring to react at the constant temperature of 30 DEG C for 20-60 minutes, wherein the pretreating agent is a mixture of organic flocculent and demetallizing agent in a ratio of (0.5-1.5):1 (m/m); 3) carrying out atmospheric flash evaporation on the reaction product in a distillation kettle, gradually heating in a nitrogen atmosphere to sequentially distil out light hydrocarbons, water and gasoline, and finally controlling the kettle temperature at less than 200 DEG C to remove the light hydrocarbons, moisture and gasoline; and 4) carrying out centrifugal slag removal treatment to obtain the pretreated oil.