The kinetic modeling of styrene controlled radical polymerization, initiated by 2,2’-asobis(isobutirnitrile) and proceeding by a reversible chain transfer mechanism was carried out and accompanied by “addition-fragmentation” in the presence dibenzyltritiocarbonate. An inverse problem of determination of the unknown temperature dependences of single elementary reaction rate constants of kinetic scheme was solved. The adequacy of the model was revealed by comparison of theoretical and experimental values of polystyrene molecular-mass properties. The influence of process controlling factors on polystyrene molecular-mass properties was studied using the model.