The modified nano WS2 was added to the rapeseed oil and the stability of the oil sample was tested. The tribological properties of rapeseed oil with different nano-WS2 content were investigated by fourball tester.The results show that modified nano-WS2 has good dispersion stability in rapeseed oil.Nano-WS2 can improve the lubrication performance of rapeseed oil,and within a certain range,the higher the content of nano-WS2,the smaller the friction coefficient and wear spot diameter.At the same dosage of nano-WS2 the antiwear and friction reduction effect of nano-WS2 is more obvious under higher pressure,it shows that nano-WS2 has good extreme pressure lubrication performance.The surface morphology,typical element content and chemical state of the wear surface of steel ball were analyzed by scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS)and X-ray photoelectron spectroscopy(XPS).The results show that nano-WS2 is adsorbed on the surface of the steel ball and participates the tribochemical reaction,and the boundary lubrication film composed of WS2,WO3,Fe2O3 and FeSO4 is formed.