The present invention relates to resin composite materials, and more particularly, to low-dielectric resin composition and prepreg, resin film, resin coated copper, laminate and printed circuit board formed therefrom. The low-dielectric resin composition includes a phosphorus-containing flame retardant as shown in formula (I) and a resin with an active unsaturated bond. The low-dielectric resin composition may further be manufactured as a prepreg, a resin film, a resin coated copper, a laminate, or a printed circuit board, having a high glass transition temperature, low dielectric property, halogen-free flame retardancy and low percent of thermal expansion of laminate.