Abstract: In order to understand the characteristics and sources of ozone (O₃) pollution in Beijing in summer, the Integrated Source Apportionment Method (ISAM) of the Community Multiscale Air Quality model (CMAQ) was applied to numerically simulate the near-surface O₃ concentrations and their source contributions in different regions of Beijing in June 2019. The contributions of 14 types of NO_x and VOCs emission sources from Beijing City, Tianjin City, Hebei Province, provinces outside Jin-Jing-Ji Region and the global sources (contribution from outside the simulation area) to O₃ pollution in different regions of Beijing was quantified. The results showed that: (1) There were significant differences in the sources of O₃ and its precursors in different regions of Beijing. Both NO_x and VOCs in urban and suburban areas are mainly derived from local emissions in Beijing. The contribution of NO_x emitted by local sources to urban and suburban areas (39.7%-46.4%) was significantly greater than that of outer suburban areas (19.9%-38.8%), and the contribution of local sources to VOCs in urban and suburban areas (51.1%-75.8%) was greater than that of outer suburban areas (19.5%-39.6%). (2) NO_x and VOCs concentrations in remote suburban areas were more susceptible to the non-local emissions. (3) O₃ was mainly derived from the contribution of boundary transport, including the simulated extra-regional region as well as global background, and the contribution of boundary transport to different receptor areas in Beijing exceeded 52.6%. (4) The contribution of local source emissions to O₃ in urban and suburban areas of Beijing (6.8%-18.3%) was greater than that of outer suburbs (2.4%-7.6%), while emissions from regions outside Beijing-Tianjin-Hebei contributed to the outer suburbs of Beijing (5.2%-6.4%) was greater than the contribution to urban and suburban areas (2.7%-4.4%). It indicated that the outer suburbs had relatively small local emission characteristics and were susceptible to the blocking of Yanshan and Taihang Mountains in the north. Due to the geographical location and topographical factors, there were some differences in the contribution of different source areas in Hebei Province to different regions of Beijing. According to the research, the control of O₃ pollution in Beijing should take into account the differences in O₃ sources in urban and suburban areas, and do a good job in joint prevention and control in the surrounding areas.