A disclosed nanometer running-in agent is composed of the following compositions in percent by weight: 10-20 parts of heavy alkyl benzene, 10-20 parts of alkyl naphthalene, 20-50 parts of boronized polyisobutylene succinimide, 20-40 parts of molybdenum dialkyldithiophosphate, 1-2 parts of oil-modified phenolic resin, 1-4 parts of hydroxyl silicone oil emulsion 305, 1-4 parts of beef tallow, and 1-4 parts of detergent LD-1. The agent is prepared according to the following steps: (1) putting heavy alkyl benzene into a blending kettle, heating to 60 DEG C, and stirring for 30 min; (2) then adding boronized polyisobutylene succinimide, and continuing to stir for 30 min; (3) then adding molybdenum dialkyldithiophosphate, cyclically stirring for 120 min, then adding oil-modified phenolic resin, hydroxyl silicone oil emulsion 305, beef tallow and the detergent LD-1, keeping a constant temperature of 60 DEG C for 60 min, and then slowly cooling to 40 DEG C or less, loading a barrel, and capping, so as to obtain the agent. Compared with the prior art, the agent possesses the substantial advantages that the agent is applicable to lubrication systems of various vehicles, ships, petroleum chemical machinery, mine machinery and other large-scale equipment, and possesses multiple functions of reducing wear, reducing oil consumption, restoring wear surface, improving bearing capability, reducing noise and the like.