The invention relates to a preparation method and use of a lignin sulfonate-bentonite composite particle retention agent. The preparation method comprises adding crushed bentonite raw ore into a sodium carbonate-lignin sulfonate solution, adding water into the solution until a bentonite mass concentration is in a range of 20-80%, and carrying out extrusion sodium modification treatment by a screw extruder to obtain the lignin sulfonate-bentonite composite modified particles. In paper production, cationic polyacrylamide is added into paper pulp according to a use ratio of 0.02-0.1% before bentonite addtion, and then the lignin sulfonate-bentonite composite modified particles are added into the paper pulp according to a use ratio of 0.05-0.5% before or after pressurized screen addition. The invention provides the novel modification method of the lignin sulfonate-bentonite composite particle retention agent. The method improves lignin sulfonate-bentonite composite particle retention agent quality and improves retention and drainage performances of the retention agent in papermaking.