Abstract: Polyacrylonitrile (PAN) can be polymerized via atom transfer radical polymerization (ATRP） in a controlled way using acrylonitrile(AN) as monomer, ethyl 2-bromoisobutyrate(EBiB) as initiator and CuBr/1,10-phenanthroline as catalytic system. The influence of the dosage of initiator and catalytic system on the conversion of AN was studied by mass method. Then, in the polymerization of PAN-b-PHEA block copolymer by ATRP reaction , 2-hydroxyethyl acrylate (HEA), PAN-Br, CuBr, N,N,N′,N″,N″-pentamethyl-diethylenetriamine (PMDETA) were used as the monomer, macroinitiator, catalyst, respectively. The structures of polymers were characterized by FT-IR, 1H-NMR and element analysis. And the thermal decomposition behavior of PAN-b-PHEA block copolymer was studied by TG techniques. Results showed that the polymerization of AN by ATRP was first-order reaction when n（AN）/n（EBiB）=100，n（CuBr）/n（AN）=1%（the linearly dependent coefficient of ln(c0/ct) vs t was 0.988）. The thermal decomposition temperature of PAN-b-PHEA block copolymer was 250 °C.