Abstract: Reasons causing the instability for long-term operation of liquefied gas amine desulfurization in the light hydrocarbon fractionation unit were investigated. It was determined that the amine foaming and LPG copper corrosion below the standard cause the instability. The effects of the two critical factors were studied in details in this paper. The analysis showed that the amine foaming resulted from the dirtiness of desulfurization system, LPG containing methanol, the accumulation of the salt with high heat-stability and operation fluctuation. The copper corrosion of LPG below the standard resulted from amine entering LPG and a certain amount of organic sulfur and elemental sulfur not being removed from LPG. According to the analysis of the causes, the corresponding solutions were proposed.