Cu(0)-mediated reversible deactivation radical polymerization (Cu(0)-mediated RDRP) has been demonstrated as an excellent technique to control the polymerization of multiple vinyl monomers (e.g., acrylates, methacrylates, and styrene). However, the complexity of the reaction mechanism and multi-component system nature make it challenging to choose the appropriate conditions and consider the factors of achieving controllable polymerization when switching from one monomer to others with different reactivities. Herein, by polymerizing two examplary monomers: methyl methacrylate (MMA) and styrenevia Cu(0)-mediated RDRP under different conditions, we have found that the reaction parameters (e.g., initiator, ligand, solvent, and deactivator) play a crucial role in regulating two equilibriums: (i) mutual conversion of different copper species which determines the relative concentration of Cu(I) and Cu(II), and (ii) polymerization equilibrium which is the combination of activation/deactivation, propagation and termination processes. We have demonstrated that by taking both the mutual conversion of different copper species and the polymerization equilibrium into account, the optimal reaction conditions could be selected, and the well-controlled Cu(0)-mediated RDRPs of methyl methacrylate and styrene were achieved with narrow molecular weight distributions and predicted molecular weight.