The invention relates to a compound polymerization inhibitor and its application in a styrene rectification system and belongs to the field of chemical production. The compound polymerization inhibitor comprises two components A and B, and an organic solvent. The component A is sodium ditridecyl sulfosuccinate, and the component B is N, N-diisopropylethanolamine. The organic solvent is ethylbenzene or styrene. Through the synergistic action of the components A and B, the polymerization inhibiting effects are improved, a tar yield is increased, a styrene yield is increased, the accumulation andadhesion of the formed styrene polymer are reduced, the risks of pipe blocking caused by a polymer and reduction of the heat exchange efficiency of the heat exchanger are reduced, the safe, stable and long-term operation of the styrene device is guaranteed and the economic benefits are improved.