Abstract: TE Model 49C ozone(O₃) analyzer was used to continuously monitor surface ozone at Shangdianzi from Jan.1 to Dec.31,2004.The variation characteristics of surface ozone concentration and the relationship between O₃ concentration and meteorological elements were analyzed and,particularly,a high O₃ concentration day was identified and checked.The results show that surface ozone concentration at the background station has clear seasonal and diurnal change rules and has close relationship with local meteorological conditions.The main features include: ① O₃ concentration is high in early summer(the monthly average is maximum in June,with maximum hourly average of 129.7 μL/m³) and low in winter(the monthly average is minimum in Dec.,with maximum hourly average of 32.7 μL/m³);② Diurnal variation of surface O₃ concentration is also obvious,especially in summer.The minimum and maximum O₃ concentration appears in the morning during 4:00—7:00 and in the afternoon during 15:00—18:00 local time,respectively;③ Air temperature has significantly positive correlation with O₃ concentration.In summer,relative humidity has significantly negative correlation with O₃ concentration.Also,the wind direction and radiation correlates significantly with O₃ concentration and its variations.