The invention relates to a textile size. The textile size comprises a monomer mixed solution, small materials and process water, wherein monomers comprise 25 kg of acrylic acid, 85 kg of methacrylic acid, 80 kg of butyl acrylate, 70 kg of ethyl acrylate, 540 kg of methyl acrylate and 235 kg of methyl methacrylate; the small materials comprise 4.5 kg of an emulsifier, 8.5 kg of an initiator, 15 kg of a foam killer, 3 kg of a static inhibitor, 10 kg of a penetrant, 95 kg of ammonia water and 450 kg of alcohol. The invention further discloses a preparation method of the textile size. The textile size belongs to (pure acrylate and) co-polymerized anionic compounds, has favorable mechanical stability, is suitable for weaving high-grade fabrics, particularly (superfine polyester and polyamide fabric silks) water spraying and air-jet loom dressing, has good water solubility, permeability and antistatic property and strong cohesive force, enhances the silk traction force after silk dressing, is resistant to friction, clear in opening, free from size shedding, convenient to use and less in environmental pollution, and meanwhile, can reduce the desizing cost and the environmental impact of an afterfinish factory.