Since the discovery of high-temperature superconductors in 1986, copper-oxide superconductors have attracted widespread attention in the fields of physics and materials science due to their unique properties. This study uses first-principles calculations to explore the effects of oxygen deficiency on the optical properties of the high-temperature superconductor YBa₂Cu₃O₇ (YBCO₇) from an electronic perspective. The aim is to compare the dielectric function, optical reflectivity, and optical absorption of YBCO₇ and YBa₂Cu₃O₆ (YBCO₆), focusing on the influence of oxygen content under various frequencies. The dielectric function analysis shows that YBCO₇ has a higher polarization capability and can store more electrical energy compared to YBCO₆. Differences in photon frequency lead to variations in the dielectric function, highlighting distinct characteristics in energy absorption and reflection. Optical reflectivity and absorption studies indicate that YBCO₇ generally exhibits higher reflectivity and absorption than YBCO₆, with significant changes observed across different THz frequency ranges. The optimal frequency range for enhancing reflectivity and absorption is between 4700 and 5700 THz. The presence or absence of oxygen significantly affects the electronic structure and optical properties of these materials. This study provides valuable insights into how oxygen content and frequencies influence the optical and dielectric properties of YBCO materials, with important implications for their applications in optoelectronics and superconducting technologies.