The Ti-Al-Fe-Mn thermodynamic database was optimized by Calphad method. Based on this database the beta transus temperatures of four ternary systems in Ti-Al-Fe-Mn system was calculated and they were good agreement with experimental values. In this way the reliability of Ti-Al-Fe-Mn quaternary systems was verified. Then α+β/β phase transformation temperatures of a series titanium alloys were calculated by Calphad method and compared with values that previous formulas calculated. Also, a more accurate formula was established based on the values calculated. This results may provide a feasible way for the determination of titanium beta transus temperature.