Abstract: Diethyl polysulfides as mixed sulfiding agent were synthesized by using industrial sulfur from refining enterprises, sodium sulfide and bromoethane in the presence of phase transfer catalyst tetrabutylammonium bromide. The influences of reaction conditions on sulfur content were studied and the synthesis reaction mechanisms were discussed. The results showed that the ring-opening of S₈ molecules was the key step of the synthesis reaction and the addition of sodium sulphide greatly reduced the activation temperature of S₈. When the molar ratio of S to Na₂S was 4:1, the first step reaction temperature was 50 ℃, the first step reaction time was 25 minutes, the second step reaction temperature was room temperature, the second step reaction time was 1.5 hours and the TBAB molar fraction was 4%, the mass fraction of sulfur in diethyl polysulfides reached 63.86%, the flash point was 83.5 ℃ and the oil solubility was good.The reaction has advantages of wide raw material sources, simple synthetic route, mild reaction conditions and environmental friendliness, which has a good development and application prospects.