Acrylic fiber is commercially produced by free radical polymerization, initiated by a redox system. The fact that the kinetics is a great deal more complicated than that of ordinary polymerization systems makes the problem of controlling molecular weight a difficult one. In this study, dynamics and control of continuous acrylonitrile polymerization are studied based on a previously described kinetics by Peebles (Applied Polymer Science, 1973, 17, 113-128). As the conventional feedback controller was found to be unsuccessful, a model state feedback (MSFB) control strategy was implemented. The performances of linear and nonlinear controllers have been compared via simulation, and it was concluded that the nonlinear form would be effectively employed for set point tracking as well as disturbance rejection.