The invention provides a two-step fibering method for crop straws and application of the two-step fibering method, and belongs to the technical field of renewable resource utilization. The two-step fibering method comprises the following steps that 1) a chaffcutter and a biomass granulator are selected for later use, wherein the biomass granulator is a flat-die granulator or a ring-die granulator with a pored template and a toothed compression roller, the aperture of the pored template is 1-10 mm, the tooth depth of a toothed compression shaft is 0.1-5 mm, the tooth interval is 1-10 mm, and the granulating power of the biomass granulator is 0.1-1 times of the rated power of the biomass granulator; 2) the crop straws are cut into short straws which are 0.5-20 cm long by the chaffcutter; and 3) the short straws are placed in the biomass granulator to be extruded by a plate roller to manufacture a flocculent fabric. The two-step fibering method and the application have the advantages that the straw fibering treatment method is simplified, the efficiency is improved, exhaust gas, waste water and solid wastes are not generated when the straws are treated, the environment is not polluted, and convenience is provided for follow-up resource, fertilizer and substrate utilization.