The invention relates to a preparation method for an inorganic nano lubricating additive for plastic processing, belonging to the field of preparation of plastic lubricants. The invention provides a preparation method for an inorganic nano lubricating additive for plastic processing. The method specifically comprises steps of (1) uniformly mixing aluminum alkoxide, alcohol and water according to amolar ratio of 1:(23-45):(55-100), reacting for 3-5 hours at 65-80 DEG C, cooling to room temperature, so as to obtain an aluminum sol; and (2) uniformly mixing the aluminum sol with fluorocarboxylicacid according to a weight ratio of 1:(0.3-0.45) so as to form a sizing agent, sand milling, ultrasonic dispersing, and spray drying so as to obtain the inorganic nano lubricating additive. The prepared inorganic nano lubricating additive is used for processing plastic, and has excellent processing fluidity, high toughening and strengthening performance and high luster.