Well-defined polyacrylonitrile (PAN) copolymers containing pendant 2-ureido-4[1H]-pyrimidone (UPy) units have been synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. Copolymer compositions determined by H-1 NMR spectroscopy were in good agreement with the monomer feed. The obtained copolymers showed excellent controllability with M(n,GPC)s and M-w/M(n)s. Moreover, the dynamic adsorption properties of the copolymer for Hg2+ were investigated, indicating its potential as an efficient adsorbent to adsorb heavy metal ion.