A generalized rate model for free radical copolymerization was proposed. It can be applied not only to the system with the participation of charge-transfer complex (CTC), but also to the system without the participation of CTC. The effects of equilibrium constant, total monomer concentration, home-propagation parameters and reactivity ratios on free monomer, CTC, overall rates, and the contribution of CTC were considered in the simulation. North equation of copolymerization rate as a special case can be derived from the generalized model.