Using the mesoscale numerical weather prediction model and the air quality model along with its adjoint model (WRF-CMAQ/ADJOINT model), a simulation was conducted for a 10-day continuous ozone (O3) pollution event in Hainan Province in September 2019 (from September 21 to 30). The simulation aimed to perform source apportionment for the O3 pollution event, quantifying the contributions of different regions and species emission sources to the O3 pollution event. The results show that during this pollution event, the mean value of MDA8-O3 (ozone daily maximum 8-hour average concentration) was 167 μg·m-3, with the peak concentration of MDA8-O3 reaching 186.1 μg·m-3. The WRF-CMAQ/ADJOINT model showed a good ability to simulate the variation of O3 concentration during this pollution event in Hainan Province. The ADJOINT model indicated that long-distance regional transport was the main source of O3 pollution during this event, with an average contribution of 85% from external emissions and an average contribution of 15% from local emissions. The contribution of external emissions from Hainan Province was concentrated in the Pearl River Delta region. Analyzing the sources of VOCs emitting species, isoprene has the highest contribution among the VOCs emission sources, with an average contribution share of 51%. During the O3 pollution event, the ozone pollution regime in Hainan was mainly controlled by NOx, with only Haikou City in a zone requiring coordinated control of VOCs and NOx. Given that long-distance regional transport was the main source of the O3 pollution event, future joint control between Hainan and the Pearl River Delta region are crucial for improving air quality in Hainan.