Nano titanium dioxide (TiO2),as an excellent photocatalyst in the field of environment and energy and a new nano engine lubricating oil additive,has attracted more and more attention.The research and application progress of nano TiO2 composites in photocatalysis under different doping modes,and the research and application progress of nano TiO2 and its composites as lubricating oil additives were reviewed.The research status that comprehensively consider the photocatalytic and antifriction properties of nano TiO2 composites was summarized.It was pointed out that when nano TiO2 and its composites were used as engine lubricating oil additives,their photocatalysis and antifriction properties should be comprehensively considered,so as to reduce pollutant emissions while reducing friction.