Triphenylmethane (TPM) was successfully employed for the reverse atom transfer radical polymerization (RATRP) of methyl methacrylate (MMA) in the presence of CuCl2/pentamethyldiethylenetriamine (PMDETA). The conventional free radical polymerization (CFRP) of MMA was firstly carried out in the presence of TPM, proving that TPM can initiate the polymerization. The RARTP of MMA in cyclohexanone (CHO) exhibited the living/controlled characteristics: the first-order kinetics with respect to monomer, linear increase of number-average molecular weight (M-n) with conversion, narrow polydispersity index (PDI) (< 1.4) and successful chain extension. The possible mechanism was also proposed.