Five kinds of lubricating oil dispersion systems including 1% 5% weight of nano montmorillonite (MMT) were prepared by adding nano-MMT modified by coupling agent KH550 in the 150N base oil. The anti wear and friction reducing behaviors of the lubricating oil dispersion systems were investigated on the MMU-10G friction-wear tester with 45 steel as tribo pair, the morphology and the element of the worn surfaces were analyzed by SEM and EDX. The results show that the lubricating oil dispersion system with 3% weight of nano-MMT has the best anti wear and friction reducing behavior, it can decrease the wear mass loss of the steel tribo pair by 45.5% compared to the base oil system. The self repairing film containing the characteristic elements of MMT and Fe element is formed in the friction surface of the samples, which can compensate the wear mass loss of the steel tribo pair. The concentrations of characteristic elements of MMT are the highest in the friction surface of the sample when lubricated by the lubricating oil dispersion system with 3% weight of nano-MMT, so the wear rate of the sample is minimum. The average friction coefficient of nano-MMT lubricating oil dispersion systems is lower than that of the base oil, the difference of nano-MMT content has the unobvious effect on improving the friction reducing behavior of steel tribo pair.