Abstract: Quantitative evaluation of the health impacts of reducing indoor and outdoor O₃ levels is crucial for O₃ pollution control. Based on the differences in indoor and outdoor O₃ concentrations, this paper used city-specific exposure factors and exposure-response models to simulate and predict the health benefits of meeting different indoor and outdoor air quality standards. The results indicated that: (1) In 2020, the number of all-cause mortalities attributed to short-term and long-term exposure to O₃ pollution in 337 prefecture-level and above cities in China were 44,400 and 137,237, respectively. The corresponding economic losses were 237.5 billion RMB and 736.7 billion RMB, respectively, accounting for 0.23% and 0.73% of the country′s GDP of that year, respectively. (2) Meeting the current Indoor Air Quality Standard (GB/T 18883-2022) (160 μg/m³) and Assessment Standard for Healthy Building (T/ASC 02-2021) (112 μg/m³) of O₃ cannot bring health benefits. When the daily indoor O₃ standard concentration in cities were 60, 40, 30, 20 and 10 μg/m³, the avoidable all-cause mortality losses (long-term exposure) were 90, 3,931, 16,191, 48,861 and 85,584 cases, respectively, and the corresponding avoidable economic losses were 7×10⁸, 255×10⁸, 971×10⁸, 2,787×10⁸, 4,681×10⁸ RMB, respectively. (3) When the daily outdoor O₃ standard concentration in the city were 160, 100, 80, 70 and 60 μg/m³, the avoidable all-cause mortality losses (long-term exposure) were 6,044, 46,090, 78,888, 100,160, 124,649 cases, respectively, and the corresponding avoidable economic losses were 355×10⁸, 2,548×10⁸, 4,298×10⁸, 5,420×10⁸ and 6,700×10⁸ RMB, respectively. The research results show that reducing indoor O₃ concentration can effectively reduce ozone-related health effects and economic losses. It is recommended that Shandong Province, Henan Province, Jiangsu Province, Guangdong Province and other regions implement stricter regional O₃ air quality standards as a priority.