The poly(methyl methacrylate) with single-caped halogen (PMMA-Br) was synthesized by atom transfer radical polymerization (ATRP) method under ultrasonic irradiation, with ethyl α-bromopropionate as the initiator and CuBr/2, 2-bipyridine (BPy) as the catalyst. Then the block copolymer poly(methyl methacrylate)-b-polystyrene was synthesized in cyclohexanone solution containing styrene as comonomer and PMMA-Br as the macromolecular initiator as same as the above synthesis condition. Nano-copper/poly(methyl methacrylate)-b-polystyrene composites was successfully prepared by NaBH4 as reductant in the polymerization system. The homopolymer, copolymers, and nanocomposites were characterized by means of FT-IR, 1H NMR, GPC, XRD, XPS, and TEM, and the results showed that the molecular weight of the block copolymer was controlled, and there existed interaction between copper particles and PMMA chain, and that ordered-assembly behaviors of block copolymer, induced by the nano-copper, were investigated by HTEM.