In order to develop a solvent with satisfied organosulfur removal performance for high sour natural gas, the absorption process using UDS and MDEA as solvents was investigated and the absorption model was established to evaluate the selectivities of the two solvents for organosulfurs. The results indicate that both of the solvents, UDS and MDEA, have excellent absorption performance for H2S and CO2. The solvent, UDS, shows evident advantages when adsorbing high content COS and mercaptans. From the viewpoints of the solubility and the mass transfer performance, COS is the most easily absorbed. The methyl mercaptan and ethyl mercaptan come after. The isopropyl mercaptan and n-propyl mercaptan are hard to be absorbed. Compared with MDEA, the solvent UDS shows lower Henry constants and greater mass transfer factors for the organosulfurs; therefore, it has higher solubility and better mass transfer performance for the organosulfurs.