Proton-decoupled，partially relaxed，Fourier-transform NMR of 13C (operating at 50.3 MHz) in natural abundance was used to determine spin-lattice relaxation times (T1) and nuclear Overhauser effect (NOE) of individual carbon of a serier of 1

2-polybutadienes with different 1

2-unit content in solution．The microstrueture depen-dence of molecular motion and the internal motion of vinyl group in 1

2-polybutadiens have been studied by T1 and NOE．The nT1 values for carbons in cis-1，4-units were about twice as large as those for earbons in main chain of 1

2-units with the same se-quence strtmture，the nT1 values far carbons in the saine unit

become larger when the adjacent 1，2-units are replaced by 1

4-units and the nT1 values decrease sharply with increase of 1

2-unit content in the polymer．Form above it was seen that vinyl group has a intense steric hindrance for molecular motion of 1

2-polybuCadiene．The fact that nT1 values for CH is larger thanthose for CH2 in vinyl group implies that there are complex internal motion of vinyl group．It has been shown by caleula-tion that the dominant factor causing the difference in nT1 of CH and CH2 in vinyl group is its swinv in a plane perpendicular to the chain backbome．