The hyperbranched copolymers were obtained by the atom transfer radical copolymerization of p-(chloromethyl)styrene (CMS) with N-cyclohexylmaleimide (NCMI) catalyzed by CuCl/2,2Π-bipyridine (bpy) in cyclohexanone (C 6 H 10 O) or anisole (PhOCH 3 ) with CMS as the inimer. The influences of several factors, such as temperature, solvent, the concentration of CuCl and bpy, and monomer ratio, on the copolymerization were subsequently investigated. The apparent enthalpy of activation for the overall copolymerization was measured to be 37.2 kJ/mol. The fractional orders obtained in the copolymerization were approximately 0.843 and 0.447 for [CuCl] 0 and [bpy] 0 , respectively. The monomer reactivity ratios were evaluated to be r NCMI Ο 0.107 and r CMS Ο 0.136. The glass transition temperature of the resultant hyperbranched copolymer increases with increasing f NCMI , which indicates that the heat resistance of the copolymer has been improved by increasing NCMI. The prepared hyperbranched CMS/NCMI copolymers were used as macroinitiators for the solution polymerization of styrene to yield star-shaped poly(CMS-co-NCMI)/polystyrene block copolymers by atom transfer radical polymerization.