Abstract: 25MHz Carbon-13 NMR spectra were used to study end group and branched structure of H₂O₂-initiated liquid hydroxy terminated polybutadiene (HTPB) obtained in ethanol.The carbon-13 spectra of the three main primary alcohols have been assigned. Recognition of RCH:CHCH₂OH(Ⅰ) and RR C:CH₂OH(Ⅱ) resonances strongly supports the stru-cture Ⅰ and Ⅱ. The ethanol used as solvent in polymerization may be introduced into polymer, forming end group structure, dominantly RCH:CHCH₂CH(OH)CH₃ (cis and trans). Its hydroxy content was about 8% of total hydroxy amount in HTPB. Some terminal alcohol, aldehyde groups and branched structures have also been determined,but their contents were minor in HTPB.