The invention discloses a preparation method of an aramid composite. The method comprises the steps as follows: (1) preparation of aramid base cloth: meta-aramid staple fibers are used and are subjected to spinning, doubling and warping, and the aramid base cloth is woven on a rapier loom; (2) preparation of a dipping finishing agent: sodium hydroxide, resorcinol and formaldehyde are put into a reaction container and evenly mixed, then a catalyst is added, materials are heated and react to release heat, and the materials are boiling, are continuously heated to keep boiling and then are subjected to reduced-pressure dehydration; (3) a padding process: the dipping finishing agent is added to a dipping tank of a finishing machine and is treated onto the aramid base cloth through a single-dipping-single-rolling technology, and then the aramid base cloth enters a drying oven to be dried and cured. According to the method, the technology is simple, reaction conditions are not harsh, the aramid base cloth is prepared from the meta-aramid staple fibers, is subjected to technological treatment by the aid of the dipping finishing agent and is finally dried and cured, the composite is obtained, the quality of the product is stable, the preparation cost is low, the purity and the yield of the product are high, and industrial production is facilitated.