The Tween80/n-alkanol (C2~C8)/ethyl butyrate/water four-component microemulsion system was simulated using the dissipative particle dynamics (DPD) method. Effect of n-alkanol concentration and n-alkanol alkyl chain length on the phase behavior and microstructure during the formation of microemulsion was also studied. The simulation results indicated that the concentration and alkyl chain length of n-alkanol greatly affected morphological changes in the self-assembly of the system. When the n-alkanol concentration was low, particle size of the microemulsion increased with an increase in alcohol concentration. After the n-alkanol concentration was increased to a certain extent, a further increase in concentration led to a change in the structure of microemulsion from spherical shape to pipe-like and net-like shapes. A comparison of the n-alkanol concentrations when morphological changes occurred in microemulsion systems with different alkyl chain lengths revealed that an increase in alkyl chain length of n-alkanol promoted morphological changes in the microemulsion system at low n-alkanol concentrations and the interfacial tension of the system stabilized rapidly. In addition, the results showed that increasing chain length of alcohol increased the water/oil (W/O) and bicontinuous microemulsion region of Tween80/n-alkanol (C2~C8)/ethyl butyrate/water system. This result provides guidance for the control of type, morphology, and size of the microemulsion system, to thus achieve selective extraction of proteins.