The invention provides a synthetic method of 4,4'-sulfonyl bis[2-(2-propenyl)]phenol, a thermal display agent, 4,4'-diallyl diphenyl sulfone is directly in the 4,4'-sulfonylbis[2-(2-propenyl)]phenol is prepared by heating rearrangement in an organic solvent. In the process of preparing 4,4'-sulfonylbis[2-(2-propenyl)]phenol in the present invention, by using a Lewis acid catalyst, high-temperature reactions above 200 degrees can be avoided, safety accidents can be greatly reduced, energy can be saved, consumption can be reduced, and Reduce equipment investment. The catalyst zinc chloride, aluminum trichloride, iron trichloride and titanium tetrachloride used in the process of preparing 4,4'-sulfonyl bis[2-(2-propenyl)]phenol in the present invention have low cost and can be post-treated convenient. In the process of preparing 4,4'-sulfonyl bis[2-(2-propenyl)]phenol, the present invention can avoid the use of high-boiling point solvents and heat-conducting oil, and greatly reduce production costs.