The invention discloses a thin felt with glass fiber for the substrate of plastic floor ant the manufacturing method, comprising short-cut silk of glass fiber, dispersant, surfactant and organic binder. Said short-cut silk of glass fiber is middle-alkali or non-alkali, the diameter is 9-10 mum and the length is 6-12mm. Said dispersant is thickener belonging to cellulose acetate. Said surfactant is quaternary ammonium cationic surfactants. The organic binder is the mixture of polyethylene acetate emulsion thermosetting resin, KH560 coupling agent and water. Said thin felt with glass fiber is produced by wet technology, which comprises producing stock, preparing slurry, sizing forming, dipping and drying so on. The product is provided with high compactness, even thickness, widely applied temperature, and no-deformation under high temperature. The plastic floor surface with the felt as the substrate, is provided with flat and smooth, no shrinkage deformation, no-bending, no mildewing and stable dimension.