Abstract: Solubility data for the ternary system ethylene/iso-pentane/PE and ethylene/n-hexane/PE were determined for PE crystallinity 48.6% at temperatures of 70—90℃ and pressures up to 2MPa with the partial pressures of iso-pentane 80—190 kPa and those of hexane 20—90 kPa.Compared with the solubility data of the binary system, the effects of the ternary system were discussed with respect to the partial pressure of the second component and temperature.It was shown that as the results of dilation and interaction between low-molecules, the presence of iso-pentane or n-hexane gave rise to an increase in the solubility of ethylene whereas the presence of ethylene decreased the solubility of iso-pentane or n-hexane.The higher the partial pressure of the second component, the more the impact on the solubility of the first one.The impact increased with decreasing temperature and increasing partial pressure of the first component.The solubility of ethylene in the ternary system could be described by Henry’s law whichwas similar to the binary system. Flory-Huggins model was satisfactory for fitting solubility data of both iso-pentane and n-hexane, especially the former.