Abstract: In this paper, a highly sensitive detection method - polarized cavity ring-down (P-CRD) technique - is employed to investigate the influence of deposition angle on the optical loss and stress-induced birefringence of single-layer SiO₂ films prepared with specific deposition process parameters. The P-CRD technique is based on measuring the decay behavior of accumulated polarized light reflecting back and forth inside a resonant cavity. The decay time and oscillating frequency of resulted phase difference of the CRD signal are applied to measure simultaneously the absolute values of the optical loss and residual stress-induced birefringence at the same measurement point of single-layer SiO₂ films. In the experiment, the optical losses and stress-induced birefringence of the single-layer SiO₂ film samples prepared under different deposition angles of 60°, 70°, and 80° are measured and analyzed. The results revealed the effects of the changes of surface roughness and film compact density caused by the different deposition angles on the optical loss and stress-induced birefringence of the single-layer SiO₂ films, respectively. These results are helpful to the preparation of high-performance SiO₂ films with low optical loss and low residual stress.