A resin composition, a copper-clad laminate using the same, and a printed circuit board using the same are introduced. The resin composition comprises a specific phosphorus-containing salt and a prepolymer of vinyl-containing polyphenylene ether. The resin composition features specific ingredients and proportion to thereby achieve satisfactory properties of prepreg made from the resin composition, and attain satisfactory laminate properties, such as high degree of heat resistance and satisfactory dielectric properties, and thus is suitable for producing a prepreg or a resin film to thereby be applicable to copper-clad laminates and printed circuit boards.