The invention discloses a method for preparing high-activity fine pre-dispersion aramid fiber pulp master colloidal particles and belongs to the technical field of high molecular material modification. The method comprises the following steps of (1) pre-mixing aramid fiber pulp and a pre-processing composition to uniformly coat an in-situ modification additive (a coupler) and an osmotic isolation additive in the pre-processing composition and isolate an aramid fiber pulp sub-micron short fiber surface to obtain an aramid fiber pulp composition; (2) mixing and uniformly dispersing the aramid fiber pulp composition and a rubber carrier in an internal mixer or an opened rubber refining machine to obtain an aramid fiber pulp master rubber; (3) performing thermal treatment on the aramid fiber pulp master rubber in the internal mixer or a heating roller, and further isolating aramid fiber pulp secondary-micron short fibers; (4) extruding the thermally treated aramid fiber pulp master rubber by a single screw extrusion granulation system to obtain the high-activity fine pre-dispersion aramid fiber pulp master colloidal particles of which the content of aramid fiber pulp is 30 to 50 percent. The master colloidal product has very good dispersing performance and interface adhesion performance in EPDM (Ethylene-Propylene-Diene Monomer), SBR (styrene butadiene rubber), NR (Natural Rubber), CR (chloroprene rubber), NBR (nitrile-butadiene rubber), HNBR (hydrogenated butadiene-acrylonitrile rubber) and other rubber substrates.