Abstract: The ¹³C-NMR spectra of the alternating copolymer of isoprene with methyl mcthacrylate and its block copolymer, poly (styrene-alt-methyl acrylate) -block-poly(isoprene-alt-methyl methacrylate) -block-poly(styrene-alt-methyl acrylate), have been studied. The results indicated that all blocks of the block copolymer have completely alternating structure and the isoprene units presented mainly with trans-1,4-structure. It was observed that there were two addition modes of isoprene and methyl methacrylate, "head to head" and "head to tail", while the former was predominated.