Surface ozone (O3) in non-urban areas could be strongly influenced by regional transported air pollutants from distant urban agglomeration. Using comprehensively the polar plot graphical technique, backward trajectory and potential source contribution analyses, the variations of surface O3 and its potential source regions at an island site of Zhejiang, China was analyzed based on data from June 2013 to October 2016. Relatively high hourly O3 levels (max. 154.0 ppb) were often observed, with the total hourly O3 over national standard (75 ppb) being 583 during the study period, which indicated high health risks of O3 exposure to people. An obvious time-lag for diurnal O3 peak was observed, with the daily maxima often occurring at 16:00. A decreased O3 level was observed in summer, which was probably due to the comprehensive influences of intense rainfall, high relative humidity and clean marine airmasses during this season. External transport of air pollutants had played a dominant role in affecting local O3, with relatively high O3 concentrations (> 50 ppb) being observed under high wind speeds (> 5m s-1). Based on all the source identification analyses, the major regions contributing to surface O3 were found to lie to the north and northwest of the study area. Long-range transported air pollutants from the coastal provinces of the North China Plain could significantly enhance surface O3 at the study site, while the contributions from local and the south areas to the study site were rather weak. High incidence (64.3%) of O3 pollution was accounted for by the inflowing airmasses from outside of Zhejiang, which quantitatively confirmed the significant background transport of O3 to this province. Coordinated inter-regional control on pollutant emissions should be carried out for O3 reduction in Zhejiang Province.