During the overhaul of a butadiene unit of a petrochemical company in 2024, a large amount of black slag polymer was found in the first layer packing distributor at the top of post-wash tower for extractive distillation system, blocking the liquid distributor and affecting the separation effect of the extractive distillation system. Meanwhile, the bypass line on the tube side of solvent heat exchanger E-1130A was found to be completely filled with polymers. This paper analyzes the causes of polymer generation, and proposes some measures for preventing polymerization in the extractive distillation system combined with production practices and process control indicators, so as to extend the operation cycle of the unit.