The invention discloses a method for preparing a 
graphene water-based lubricating agent in situ, belonging to the field of application of 
graphene serving as a nanometer lubricating additive. The lubricating agent consists of 
graphene nanoparticles, a surface modifier and 
purified water. The method comprises the following preparation steps: 1, dissolving a surfactant in deionized water according to a ratio, thereby obtaining a liquid; 2, uniformly dispersing graphene 
powder in the liquid; 3, performing 
ultrasonic cavitation treatment on the graphene dispersion liquid; 4, standing the liquid for a certain time, and taking the upper liquid; 5, performing 
centrifugal separation treatment on the obtained liquid; and 6, collecting the supernatant of the centrifuged liquid, thereby obtaining the water-based lubricating agent containing graphene prepared in situ. The method disclosed by the invention is simple in feasible, and the 
dispersion stability of the graphene is high. The 
friction test result proves that according to the extremely small addition amount (0.001-1 percent) of the graphene, the anti-wear and 
friction reduction properties of the lubricating agent can be greatly improved, and excellent characteristics such as good inherent cooling property, high 
machinability and environment friendliness of the water-based lubricating agent are not influenced.