Obtaining non-contact optical temperature sensing materials with good thermal stability and luminescent properties is one of the current research hotspots. In this work, Er3+/Yb3+ co doped CaGdAlO4∶Erx,Yb0.10(x=0.006, 0.008, 0.010, 0.012, 0.014) single-phase phosphors were prepared by high-temperature solid-state method. For CaGdAlO4∶Erx,Yb0.10 powders with different Er3+ doping concentrations, the particle sizes range from 0.6 μm to 4.2 μm. When the samples are under 980 nm laser excitation, there exists two emission bands in the 500~575 nm range and one emission band in the 630~690 nm. The two stronger green emission bands located at 528 and 550 nm, and they could be attributed to 2H11/2→4I15/2 and 4S3/2→4I15/2 transitions, while the weaker red emission band at 663 nm could be attributed to 4F9/2→4I15/2 transition of Er3+. The optimal upconversion luminescence intensity was obtained from CaGdAlO4∶Er0.010,Yb0.10. In the temperature range of 300~573 K, based on fluorescence intensity ratio FIR528/550 parameters, the absolute sensitivity SA increases from 44.4×10-4 K-1(@300 K) to 52.0×10-4 K-1(@445 K), and then decreases to 49.0×10-4 K-1(@573 K). The relative sensitivity SR decreases monotonically from 0.95×10-2 K-1(@300 K) to 0.27×10-2 K-1(@573 K). Furthermore, the heating-cooling cycling experiment shows that the thermal repeatability of temperature sensing for the phosphor is better than 98%. The results demonstrate that CaGdAlO4∶Er0.010,Yb0.10 phosphors have potential applications in the field of optical temperature sensing.