In orderto improve the dispersing effect of nano carbon based additives in lubricating oil,the effects of seven dispersants,including Span20,Span60,Span80,Tween20,Tween60,oleic acid and cetyl trimethyl ammonium bromide,on the dispersion stability of nano carbon powder,nano graphite and graphene in lubricating oil were investigated.A suitable dispersant was selected by static observation method,and the optimal dispersant was determined by ultraviolet absorption spectrophotometric.The optimal ultrasonic oscillation time and the optimum addition of the dispersant were determined through ultrasonic dispersion test and dispersant dosage test.The results show that,among the seven dispersants,Span60 has the best dispersion effect for three kinds of nano carbon additives in base oil 400SN.The optimal ultrasonic oscillation time is 30 min during the configuration of oil samples.When nano graphite,nano carbon powder and nano graphene are used as antiwear additives for 400SN base oil,the optimum mass fractions of Span 60 are 1.0%,1.5% and 2.5% respectively.