The invention discloses a surface modifying agent used for chemical plating. The surface modifying agent comprises a sulfydryl silane coupling agent, alkyl polyoxyethylene quaternary/biquaternary ammonium salt, polyoxyethylene ether type nonionic surfactant and pH regulator, wherein the above components are mixed with water to form mixed solution, the sulfydryl silane coupling agent accounts for 0.5 to 5% of the total weight of the mixed solution, the alkyl polyoxyethylene quaternary/biquaternary ammonium salt accounts for 0.1 to 0.4% of the total weight of the mixed solution, and the polyoxyethylene type nonionic surfactant accounts for 0.02 to 0.1% of the total weight of the mixed solution; the pH value of the surface modifying agent is 8 to 10. The invention further discloses a surface modification treatment method applying the surface modifying agent, and a fabric chemical plating method. The surface modifying agent provided by the invention is used for surface modification treatment of fabric, is low in cost, safe, efficient, and easy to clean, and can improve the binding force of a metal plating and fabric.