Thermodynamic database of the Mo-RE (RE: Ce, Pr, Nd, Sm, Eu, Tb, Ho, Er, Tm, Yb, Lu) systemswas developed for the design of the Molybdenum-based refractory alloys. The thermodynamic calculation and optimization of Mo-RE binary systems have been performed using the Calculation of Phase Diagrams (CALPHAD) method on the basis of experimental data including phase equilibria and thermodynamic properties. The Gibbs energies of the liquid and solid solution phases are described by the sub-regular solution model, whereas those of the gas phases are described by the ideal gas model. The present work obtained a set of self-consistent thermodynamic parameters that reasonably describes the thermodynamic properties of the Mo-RE binary systems. A good agreement between calculation results and experimental data was reached. The utility of this database is demonstrated in the examples of thermodynamic calculations of the mixing enthalpy of liquid phase in the Mo-Ce and Mo-Pr system. Also, the 1200, 1300, 1400oC isothermal section diagrams of the Mo-Ho-Tb system and the related property diagrams like phase fraction of desired phases were depicted. Meanwhile, the Mo-Cu-Er ternary phase equilibria sections from 800 to 1000oC were extrapolated. These results show fairly good predictions and provide much-needed information for the alloy design of the Molybdenum-based refractory materials.