Copolymerization of α-Methylstyrene(AMS) with Acrylonitrile(AN) was carried out with benzoylperoxide(BPO) as an initiator in toluene at 80℃ in a continuous stirred tank reactor. Reaction volume and residence time were 0.6 liters and 3 hours, respectively. The monomer reactivity ratios, rAMS and rAN determined by both the Kelen-Tüdös method and the Fineman-Ross method were rAMS=0.16(0.14), rAN=0.04(0.06). The cross-termination factor Φ of the copolymer over the entire AMS composition ranged from 0.75 to 0.92. The Φ factors of poly(AMS-co-AN) were increased with increasing AMS content. The simulated conversions and copolymerization rates were compared with the experimental results. It was observed that the average time to reach dynamic steady-state was three times the residence time.