Kinetics of copolymerization of acrylonitrile(AN) with N-vinylpyrrolidone(NVP) initiated by azodi-isobutyronitrile(AIBN) was investigated in H2O/dimethyl sulphoxide(DMSO) mixture between 50degreesC and 70degreesC under N-2 atmosphere. The rate of copolymerization and particle size were measured respectively. The kinetic equation of copolymerization system is obtained as R-p proportional to c(AIBN)(0.651+/-0.123)c(AN)(1.59+/-0.35)c(NVP)(1.17+/-0.14) at 60degreesC. The overall activation energy for copolymerization system was computed as 87.3 kJ(.)mol(-1). Effect of additives of hydroquinone and dioxane on copolymerization was discussed. The polymerization is retarded by hydroquinone and accelerated by dioxane, which confirms the free radical copolymerization of AN with NVP.