As an example of the La-Mg-Y system, the method how to set up the thermodynamic model of individual phases was introduced in the process of thermodynamic optimization. The solution phases (liquid, body-centered cubic, face-centered cubic, hexagonal close-packed and double hexagonal close-packed) were modeled with the Redlich-Kister equation. The compound energy model has been used to describe the thermodynamic functions of the intermetallic com- pounds in the La-Mg-Y systems. The compounds Mg2Y, Mg24Y5, Mg12La, Mg17La2, Mg41La5, Mg3La and Mg2La in the La-Mg-Y system were treated as the formulae (Mg,Y)2(La,Mg,Y), Mg24(La,Mg,Y)4Y, Mg12(La,Y), Mg17(La,Y)2, Mg41(La,Y)5, Mg3(La,Mg,Y) and Mg2(La,Y), respectively. A model (La,Mg,Y)0.5(La,Mg,Y)0.5 was applied to describe the compound MgM formed by MgLa and MgY in order to cope with the order-disorder transition between body-centered cu- bic solution (A2) and MgM with CsCl-type structure (B2) in the La-Mg-Y system. The Gibbs energies of individual phases were optimized in the La-Mg, La-Y and La-Mg-Y systems by CALPHAD technique. The projection of the liquidus sur- faces for the La-Mg-Y system was predicted. The Mg-based alloys database including 36 binary and 15 ternary systems formed by Mg, Al, Cu, Ni, Mn, Zn and rare earth elements was set up in SGTE standard. The an example of the La-Mg-Y system, the method how to set up the thermodynamic model of individual phases was introduced in the process of thermodynamic optimization. The solution phases (liquid, body-centered cubic, face-centered cubic, hexagonal close-packed and double hexagonal close-packed) were modeled with the Redlich-Kister equation. The compound energy model has been used to describe the thermodynamic functions of the intermetallic com- pounds in the La-Mg-Y systems. The compounds Mg2Y, Mg24Y5, Mg12La, Mg17La2, Mg41La5, Mg3La and Mg2La in the La-Mg-Y system were treated as the formula (Mg, Y) 2 (La, Mg, Y), Mg24 (La, Mg, Y) 4Y, Mg12 (La, Y), Mg17 (La, Y) 2, Mg41 (La, Y) 5, Mg3 (La, Mg, Y) and Mg2 La, Mg, Y) 0.5 was applied to describe the compound MgM formed by MgLa and MgY in order to cope with the order-disorder transition between body-centered cu-bic solution (A2) and MgM with CsCl-type structure in the La-Mg-Y system. The Gibbs energies of individ The projection of the liquidus sur-faces for the La-Mg-Y system was predicted. The Mg-based alloys database 36 binary and 15 ternary systems formed by Mg, Al, Cu, Ni, Mn, Zn and rare earth elements was set up in SGTE standard.