Abstract: The ¹³C-NMR spectrum of the alternating copolymer of butadiene (BD) with methyl methacrylate (MMA) has been studied. The results indicate that the degree of alternation approches to 99.2% and the contents of trans-1,4-,cis-1, 4-and 1, 2-BD in the alternating structure units are 97.6%, 1.3% and 1.1%, respectively. It has also been proved by the ¹³C-NMR spectra that every block of the block polymer, poly[(ST-a-MA)-b-(BD-a-MMA)-b-(ST-a-MA)] has alternating structure as well.