Abstract: The tacticity of 1,2-polybutadienes Was determined by using ¹³C-NMR technique.The results obtained show that the tacticity of the molecules did not change much with the change of molecular weight. Therefore the long chain branching of 1,2-polybutadiene may be characterized by GPC-AUV technique. The long chain branching of 1,2-polybutadienes was measured by a GPC coupled with an automatic recording capillary viscometer. In this work the experimental relation [η]_(V) was translated to the calibration curve [η]_(VR) for the mono disperse samples.The curve [η]_(VR) combined with the principle of universal calibration will provide the molecular weight distribution and the average brandhing effect in the samples.