In order to obtain the thermodynamic description of the Mg-Ga binary system, the thermodynamic assessment of the system was carried out using the CALPHAD method through Thermo-calc(r) software package based on the evaluation of all available experimental data from the published literature. The solution phases, including liquid, hcp(Mg) and orthorhombic(Ga), were described by the substitutional solution model, of which the excess Gibbs energies were expressed with the Redlich-Kister polynomial. Meanwhile, all intermetallic compounds, Mg5Ga2, Mg2Ga, MgGa, MgGa2 and Mg2Ga5, were modeled as stoichiometric compounds. A set of self-consistent thermodynamic parameters formulating the Gibbs energies of various phases in the Mg-Ga binary system were obtained finally. The much better agreement is achieved between the calculated results and the reported experimental data.