The free radical bulk terpolymerization of alpha-methylstyrene/styrene/acrylic acid (AMS/ST/AA) in a continuous stirred tank reactor (CSTR) was studied over the ranges of temperature, residence time, solvent and initiator concentration, and chain transfer agent level. To determine the influence of changing monomer feeding ratios on the AMS/ST/AA bulk terpolymerizations, a series of reactions were conducted at 175℃ with AMS/ST feedinds ranging from 0/100 to 100/0 by weight. It has been found that the molecular weight (MW) of the bulk terpolymer was decreased as the reaction temperature, initiator, chain transfer agent and solvent concentration increased. Long residence time increased the MW of the bulk terpolymer.