The invention discloses a preparation method of nanometer magnesium silicate hydroxide, and a preparation method and an application of an anti-wear agent. The preparation method of nanometer magnesium silicate hydroxide comprises the following steps: 1, providing magnesium oxide and silica according to a predetermined mass ratio, and mixing magnesium oxide and silica with a predetermined concentration of a sodium hydroxide solution to obtain a mixed solution; 2, reacting the mixed solution at a predetermined temperature for a predetermined time to obtain a reacted mixed solution; 3, cleaning and filtering the reacted mixed solution until the pH value of the reacted mixed solution is smaller than 8, and filtering to obtain a filtration product; and 4, drying the filtration product to obtain the nanometer magnesium silicate hydroxide. The preparation method of the nanometer magnesium silicate hydroxide disclosed in the embodiment of the invention has the advantages of simplicity, feasibility, strong operability, and realization of the controllable synthesis of magnesium silicate hydroxide nanoparticles through controlling the reaction time.