A conventional high temperature solid state method was utilized to prepare CaO-Y2O3, which is a potential candidate for manufacturing crucible material to melt titanium and titanium alloys with low cost. Meanwhile, Yb3+ ions and Er3+ ions were selected as the sensitizers and activators respectively to dope into CaO-Y2O3, aimed at providing real-time optical thermometry during the preparation process of titanium alloys realized using fluorescence intensity ratio (FIR) technology. The results reveal that a high measurement precision can be acquired by using the Stark sublevels of Er3+ 4F9/2 to measure the temperature with a maximum absolute error of only about 3 K. In addition, by analyzing the dependence of I-4(13/2) -> I-4(15/2) transition on pump power of 980 nm excitation wavelength, it was found that the laser-induced thermal effect has almost no influence on the temperature measurement conducted by using the FIR of the Stark sublevels of Er3+ 4I13/2, which means that a high excitation pump power can be used to obtain strong NIR emission and good signal-to-noise ratio for optical thermometry without the influence of the laser-induced thermal effect. All the results reveal that CaO-Y2O3: Yb3+/Er3+ is an excellent temperature sensing material with high measurement precision.