The Gibbs free energy of liquid and crystal, intermetallic compounds, and amorphous phases were investigated by thermodynamic analysis for microstructure of high-entropy alloy (HEA). Results show that the value of ΔSrΔHh(sol.) plays an important role in estimating the microstructure of HEAs. The alloys with lower value of ΔSrΔHh(sol.) have stronger tendency of forming single fcc or bcc solid solution, and the alloy with complicated microstructure always has larger value of ΔSrΔHh(sol.).