Emulsion copolymerization of styrene and ethylene catalyzed by a series of neutral nickel(II) complexes was carried out in an aqueous system to give high-molecular-weight copolymers. The copolymers and emulsions were characterized by an array of techniques including NMR, GPC, TEM, WAXD and DSC. The results indicate that the copolymers obtained are mostly block copolymers of polyethylene with random insertion of styrene units, and their Mw is in the range of 105-106. By enhancing the electron withdrawing of the substituents on the phenoxy ring, the ethylene contents in the copolymers varied from 0 to 52%. The molecular weight distribution of the copolymers was bimodal. With reducing the steric effect of substituents on the aniline ring, the solid contents of the emulsions decreased. The polydispersity of the copolymer varied from 11.1 to 2.8, and the ethylene content in the copolymer was below 10%. The homopolymer of styrene was obtained when the substitutent on the aniline ring was hydrogen.