The invention provides a preparation method for fine rubber powder. The preparation method comprises the steps of raw material treating, grinded material mixing, grinding, wet sieving, dehydrating, drying, dry sieving and packaging. According to the preparation method for the fine rubber powder provided by the invention, pre-crushed coarse granular rubber blocks and water are sufficiently mixed, and then are grinded in a circulating mode in a closed assembly line, and automatic drying, sieving and packaging of rubber powder are realized. The preparation method is high in degree of automation, is low in cost, and can be used for preparing ultrafine-grain fine rubber powder without pollution. The fine rubber powder prepared by the preparation method is combined with the surface of a raw rubber group so as to be in canine-tooth-alternating embedding, and therefore, net-shaped contact area is greatly increased in a spatial three-dimensional direction, combination of rubber powder and virgin rubber can be remarkably improved, and combination strength, toughness and wear resistance of glue are greatly enhanced.