Abstract: Relationship between the increase of refractive index and transmissivity and the decrease of bi-refringence of optical plastics is discussed on the basis of electromagnetic theory. The molecular design and the main properties of a new kind of optical plastics-EA optical plastics are described. The material was prepared successfully by the copolymerization of bisphenol A-epoxy-diacrylate with styrene, and represents a type of good lens material, having the following properties:nD=1.5836,r=32, T (transmissivity)<90%, having low internal stress and a high resolving power.