The thermodynamic properties and phase diagram of the Pt–Ti system have been analyzed by the CALPHAD technique using a computational optimization procedure. Based on the experimental data, the solution phases (liquid, body-centered cubic (Ti), face-centered cubic (Pt) and hexagonal close-packed (Ti)) were modeled with the Redlich–Kister equation. The compounds Ti 3 Pt, αTiPt, βTiPt and γ, with a homogeneity range, were treated as sublattice-compound energy model, respectively. The compounds, Ti 4 Pt 3 and TiPt 8 were treated as stoichiometric phases. The parameters of the Gibbs energy expressions were optimized according to all the available experimental information of both the equilibrium data and the thermodynamic results. A set of self-consistent thermodynamic parameters of the Pt–Ti system have been obtained. The calculations agree well with the respective experimental data.