Through this study, we have attempted the thermodynamic analysis on the dimethyl ether(DME) separation process. And we also have completed the simulation of DME separation process as diesel alternative fuel using Aspen Plus and PRO/II with PROVISION. As an appropriate thermodynamic models, we selected NRTL liquid activity coefficient model to describe the non-ideality between DME, methanol and water. To estimate the vapor phase non-idealities, we have chosen the Peng-Robinson equation of state model. And we also use the Herny's law option to predict the solubilities of non-condensible gases like CO, CH4 in methanol solvent. Finally, we compared thermodynamic models between PRSV equation of state built-in HYSYS and NRTL with Peng-Robinson equation of state and Henry's law option built-in Aspen Plus and PRO/II with PROVISION.