The concentration of ethylene in the solvent of slurry polymerization process is important as it determines the extent of reaction, reaction temperature, heat duty, and molecular weight. In the present study, gas liquid behavior of ethylene, in the presence and absence of hydrogen, was studied in two process solvents namely, hexane and Varsol at various process pressures and temperatures. Solubility of ethylene increases with increase in pressure and decreases with increase in temperature in both the solvents. Ethylene solubility decreases with increase in carbon number of solvent at identical conditions. The presence of hydrogen strongly influences the solubility of ethylene in hexane and varsol. The solubility of ethylene in hexane decreases in the presence of hydrogen compared to its binary solubility, while the presence of hydrogen increases the solubility of ethylene in varsol compared to its binary solubility. A heterogeneous thermodynamic model based on the Chao-Seader method was adopted for modeling the solubility of ethylene, in the presence and absence of hydrogen, in hexane and varsol. Chao-Seader method uses the Redlich-Kwong equation of state for vapor phase fugacity, Chao-Seader correlation for pure component/reference state fugacity, Scatchard-Hildebrand model for liquid activity coefficient, and Lee-Kesler method for molar volume, Gibbs free energy departure and enthalpy departure of the mixtures. The model could explain the ethylene solubility closely in both solvents with the presence and absence of hydrogen over the entire range of process conditions studied.