The invention relates to a preparation method of nonwoven geotextile, and belongs to the field of building material. The preparation method comprises following steps: firstly, japanese banana leaf is subjected to cutting, and is mixed with quicklime, an obtained mixture is subjected to paving in a glass tank, sealed storage is carried out so as to realize gradual separation of mesophyll with leaf vine under alkaline conditions, boiling is carried out, and mesophyll is removed using a hairbrush so as to obtain a No.1 middle layer material; chicken feather is subjected to washing, drying in the blazing sun, bleaching and deodorization with hydrogen peroxide, and drying so as to obtain a No.2 middle layer material; waste sweaters are cut into pieces, are subjected to steam explosion treatment so as to realize broken and degradation of sweater fiber, and then are subjected to drying and combing so as to obtain a surface layer material; and at last, the middle layer materials and the surface layer material are subjected to paving in sequence, and are subjected to needling, hot pressing, cutting, and rolling so as to obtain a finished product. The nonwoven geotextile is high in strength, possesses excellent permeability performance, and can be widely used in the fields such as urban road construction; deformation is not easily caused; the service life of the nonwoven geotextile is prolonged.