The invention discloses a suede leather color fixing agent and a preparation method and application thereof, and belongs to the field of fabric after-finishing. The color fixing agent prepared with the method is applied to the fabric printing and dyeing color fixing after-treatment process, and the dry and wet rubbing fastness of fabric can be effectively improved. The suede leather color fixing agent is prepared from diisocyanate, polymer polyalcohol, an anionic hydrophilic chain extender, a micromolecular chain extender, an alkali neutralizing agent and a crosslinking agent, and the anionicmixed and crosslinked modified waterborne polyurethane neutral dye color fixing agent is obtained through a pre-polymerization reaction, a chain extending reaction, neutralization ionization, a crosslinking reaction and an emulsification reaction. The prepared color fixing agent is free of formaldehyde, no organic solvent is used in the production process, and the product is free of toxic solvents, environmentally friendly, good in stability, excellent in friction resistance, obvious in color fixing effect, simple in synthesis process, short in time, low in energy consumption and beneficial for large-scale industrialized production and promotion.