Abstract: Based on the thermodynamic principle, the relation between reaction enthalpy, Gibbs energy and temperature were deduced. Using phase graphs of Ti-Si-C, 12 reactions occurring possibly during TIG arc deposition on the titanium alloys were analyzed by thermodynamics. The thermodynamic calculation results showed that titanium can react with SiC, Si and C to forming ceramic phases of TiC and Ti₃SiC₂ and intermetallic compound of Ti₅Si₃ and TiSi₂. The theoretical analysis results showed that the phases of deposition layers can be predicted using thermodynamic analysis by changing the compositions of different raw materials on the TIG arc conditions. The experiment results showed that the prediction results were corresponding well with experiments results.