The radical homo- and eopolymerization of TMPM with various initiators have been studied．It was found that，with azo-type initiators，the polymerization proceeded readily．and an increase of the concentration of TMPM in the TMPM-styrene system raised the rate of copolymerization．While with acyl peroxied initiators，the polyme-rization was inhibited effectively because of the formation of the stable TMPM-oxyl radical．identified by ESR．This observation was further confirmed by the adsenee of inhibition effect on the addition of 2，2，6，6-tetramethyl 4-piperidinol to the poly-merization system，whereas remarkable inhibition was observed on the addition of the stable 2，2，6，6-tetramethyl 4-piperidinol N-oXyl radical．The reaction mechanism was discussed．We also found that when TMPM reacted with BPO in petroIeum ether．N-benzoy-loxy 2，2，6，6-tetramethyl 4-piperidinyl methaerylate was formed，and this novel com-pound has been characterized with IR．ESR and NMR and MASS Spectroscopy．