To synthesize effective compatibilizers for the compatibilization of acrylic polymer-silk fibroin blend fibers, the homogeneous graft copolymerization of acrylonitrile onto silk fibroin, initiated by potassium persulfate-sodium bisulfite redox system in 60 wt % ZnCl2 aqueous solution was investigated. The percentage graft, percentage efficiency, and molecular weight of the grafted polyacrylonitrile increase with the increase of the concentration of initiator, the concentration of acrylonitrile, and the temperature to optimum values, respectively, and then decrease. With the increase of reaction time, the percentage graft and percentage efficiency increase, whereas the molecular weight of the grafted polyacrylonitrile decreases. The influence of the reaction conditions on the molecular architecture of the graft copolymers is also discussed.