Abstract: A lubricating oil friction modifier and a preparation method therefor and use thereof are provided. The lubricating oil friction modifier has a chemical formula of AxBy+(C?)y. In the formula, A is a perfluoropolyether acyl group, By+ represents a cationic group having x amino groups and y ammonium ions, C? is BF4?, PF6?, AsF6?, FAP?, TFSI?, Mn2O4 or ClO4?, x is an integer greater than or equal to 1, y is an integer greater than or equal to 1, and x+y?2. The lubricating oil friction modifier has a good solubility with fluorine oil and fluorine grease, will not precipitate in the fluorine oil and the fluorine grease after being added, and can significantly improve the wear resistance of a lubricating oil such as the fluorine oil and the fluorine grease.