With the combination of nanotechnology and lubricant research and development, nanomaterials used as lubricant additives can effectively improve the tribological properties, which has been generally recognized by the industry. Under the background of the rapid development of modern machinery industry, the research progress in the development of nano-additives for lubricating oil has attracted much attention in recent years. The research on the preparation technology, material composition, properties and applications of nano-additives has made rapid progress, and a large number of related achievements have been reported continuously. Based on the research results of nano-additives applied in the field of lubricating oil development in recent years, the research progress of preparation, properties and action mechanism of nano-additives was comprehensively and carefully combed from five aspects, such as viscosity reduction, multifunctional research, compounding with commercial lubricating oil, matching special material friction pairs and adapting to extremely harsh environment. The outstanding functions and application prospects of new nano-additives were described. The new hot spots that might appear in the research and development field of nano-additives in the future were pointed out from three aspects of production preparation, property optimization and mechanism research. In the field of preparation, large-scale industrial production will be explored hard. In terms of property optimization, there is a broad space for exploration in the fields of developing multifunctional nanoparticles, enhancing commercial lubricant oil, matching special material friction pairs and adapting to extremely friction conditions. Finally, in terms of mechanism research, the viscosity reduction mechanism of nano-additives, the flow and tribological characteristics of solvent-free ionic nanofluids will also become the focus of researchers in the future.