The invention relates to a preparation method of a railway roadbed special rubber synthetic fiber geotextile; the preparation method comprises the following steps: weaving polyester/cotton canvas, drying the polyester/cotton interwoven canvas, dehairing, then calendering, carrying out double-side rubber coating, carrying out liner matting coiling, rubberizing, molding, splicing, vulcanizing, lapping seams, inspecting the seam-lapped finished product, then coiling, packing and putting in storage. The produced railway roadbed special geotextile includes a three-layer structure of an upper waterproof layer, a lower waterproof layer and middle base cloth, raised strengthening points are uniformly distributed on the lower surface of the upper waterproof layer and the upper surface of the lower waterproof layer, the service life of the product is effectively improved, and the medium maintenance period is prolonged; the geotextile is especially suitable for mechanized construction and a construction method for directly matting and layering the geotextile during bed polishing construction of a large screen scarifier, the construction efficiency of synchronously performed base bed frothing and mud rising disease treatment with combination of roadbed medium maintenance is greatly improved, and the technical support is provided for ensuring the operation quality and the operation safety of fast-speed section night construction.