Abstract: Nano-WS2 particulates were dispersed in PAO6 base lubrication oil by using the methods of ball-milling stir, ball-milling stir/surface modification and high power ultrasound/ball-milling stir/surface modification on homemade ultrasonic/ball milling experimental device, the dispersion stability of nano-WS2 particulates in base oil and the effect of surface modifier on diepersion stability of WS2 were studied, and the despersive mechanism was analysed, too. The results show that the dispersion state of the nano-WS2 particulates was best after compound action of high power ultrasonic/ball-milling stir/surface modification. The mechanism show that compound action of high power ultrasonic/ball-milling stir/surface modification could break up the nano-WS2 agglomerations and then strengthen the surfactivity of nano-WS2 particulates, and thus lead to the change of particulates′ surface characteristics from hydrophilicity to lipophilicity, After surface modifying, the long carbon chains on WS2 surface could form stereo-hindrance layer, combined with solvation layer formed by lubricant molecule, to prevent nanometer particulates from aggregate, and ultimately made nanometer WS2 particulates dispered in baseoil stably for a long time.