The effect of methylnaphthalene and polyisobutylenesuccinimide (PIBSI) on the dispersing and tribological properties of low content IF-WS2 nanoparticles in base oils were investigated.The dispersion stability and tribological properties of nano-WS WS2 lubricants in three dispersants were examined by 722 spectrophotometer and fourball friction tester.The mechanism of dispersant and WS WS2 nanoparticles was analyzed by laser particle size analyzer and infrared spectroscopy (FTIR).The results showed that methylnaphthalene possessed the optimal effect of dispersing,antiwear and friction reducing,0.01% nano WS WS2 lubricant dispersed by 4% methylnaphthalene could be stably stored for a long time,and the nano-WS WS2 lubricant had only 0.540 mm of wear spot diameter (WSD) of at 490 N and 0.11 of friction coefficient.Therefore,methylnaphthalene possesses the effect of dispersing,antiwear and friction reducing,which is due to the fact that IF-WS WS2 nanoparticles could partly dissolve in methylnaphthalene.