For development and design of SBS hydrogenation reactor, the hydrodynamic behavior of high viscosity solution in gas?liquid bubble column using SEBS-1650 hexane solution as liquid phase was studied by differential pressure method and gas disengagement method. The effects of viscosity on gas holdup of solution with low surface tension, gas holdup of large and small bubbles, rise velocity of large and small bubbles and specific surface area were investigated. With the increase of viscosity, gas holdup decreased significantly, and flow pattern directly transited turbulent regime. From the curve of gas disengagement method, three types of bubbles were identified in bubble column: large bubbles, small bubbles and fine small bubbles. The gas holdup of small bubbles and fine small bubbles gradually decreased with the increase of viscosity. Viscosity has a slight influence on the rise velocity of large and small bubbles, and the specific surface area decreased significantly with the increase of viscosity. Based on the experimental results, the formulas for calculating gas holdup of large and small bubbles and average gas holdup were listed. These results provided some necessary and reliable basic data for designing and developing a SBS hydrogenation reactor.