The invention provides a (meth)acrylate-styrene based copolymer, a composition thereof and a molding product thereof. The (meth)acrylate-styrene based copolymer comprises 10wt%-75wt% of (methyl) acrylate system monomeric unit and 25wt%-90wt% of ethylene-series monomer unit, wherein a content range of a pentamer to eleven-mer oligomers is from 500ppm tp 2000ppm.The (meth)acrylate-styrene based copolymer combines advantages of polystyrene and polymethyl methacrylate and has yellow degree and low hygroscopicity, so that the (meth)acrylate-styrene based copolymer is applicable to components of a copolymer of moldings.