Kinetic insight into photoinduced Fe-based atom transfer radical polymerization (ATRP) involving monomer-mediated photoreduction was performed by modeling approach for the first time. Preliminary numerical analysis of number-average molar mass (M-n) derivation in this specific system was given. Simulation results provided a full picture of reactant concentration and reaction rate throughout the entire polymerization. Methyl 2,3-dibromoisobutyrate (MibBr(2)) generated from methyl methacrylate (MMA)-mediated photoreduction as the leading factor for the deviation of M-n from theoretical value was confirmed by reaction contributions in -bromophenylacetate (EBPA) containing system. Reasonable predictions were made with respect to the polymerizations under a variety of initial conditions. Results show that increasing light intensity will shorten transition period and increase steady state polymerization rate; decreasing catalyst loading will cause the decrease in polymerization rate and M-n deviation; varying initiation activity will slightly increase the time to attain steady state of dispersity (M-w/M-n) evolution and enormously change the fraction of reaction contributions; increasing targeted chain length will extend transition period, decrease steady state polymerization rate, increase M-n deviation degree with same reaction contributions, and decrease the time to attain the steady state of M-w/M-n. The numerical analysis presented in this work clearly demonstrates the unique ability of our modeling approach in describing the kinetics of photoinduced Fe-based ATRP of MMA. (c) 2017 American Institute of Chemical Engineers