The invention provides granular cellulose fibers for road construction and a preparation method thereof. The granular cellulose fibers are characterized by being prepared by uniformly mixing the mixture of surfactants, mildewproof agents and water with the mixture of cellulose fibers, granulating the mixture and drying the granules, wherein the weight ratio of the two mixtures is (0.15-0.60):1; in the mixture of surfactants, mildewproof agents and water, the content of the surfactants is C1 which is more than 0 and not more than 50wt%, and the content of the mildewproof agents is C2 which is more than 0 and not more than 5wt%; and the mixture of cellulose fibers is prepared by adding an inorganic filler, a coupling agent and water to the flocculent cellulose fibers, wherein the additive amount of the inorganic filler is 0-10% (excluding 0) of the weight of the flocculent cellulose fibers, the additive amount of the coupling agent is 0-20% (excluding 0) of the weight of the inorganic filler, and the additive amount of water is 0-200% of the weight of the flocculent cellulose fibers. The invention has the following beneficial effects: the production is simple and the complex operation process and production equipment are not needed; the processing process can be completed by only a mixer and an extruder; and as effective mildewproof agents and inorganic additives are added, the hydrophobicity of the cellulose fibers is enhanced, the mildewproof property of the cellulose fibers is greatly improved and the storage lives of the cellulose fiber granules are long.