Abstract: High surface ozone concentration causes harm to human health and also affects plant growth. Ozone is a kind of important greenhouse gas and affects global climate change. In this paper, the daily, weekly, monthly and seasonal variations of surface ozone concentration under different weather conditions were analyzed based on the observation data of surface ozone concentration in Korla City, the largest city in south Xinjiang during the period from July 1, 2010 to June 30, 2012 and also the corresponding meteorological data. Moreover, the main factors affecting the variation of ozone concentration were discussed. The results were as follows: ① The daily variation curve of ozone concentration was unimodal, and the nocturnal variation was gentle but the diurnal one was significant; ② The highest value of ozone concentration occurred on Sunday and the lowest one on Wednesday; ③ The highest average monthly concentration was 82.1 μg•m^-3 and occurred in June 2011, and the lowest one was 19.2 μg•m^-3; ④ Ozone concentration in spring and summer was higher than that in autumn and winter, and the variation trend was similar to that in other coastal and mainland large and mediumsized cities; ⑤ Seasonally, the daily ozone concentration varied the most significantly in summer and spring, then in autumn, and the slightest in winter. Under different weather conditions, the daily ozone concentration varied the most significantly on sunny day, then on dust weather day, and gently on rainy and cloudy days; ⑥ The daily variation of PM₁₀ concentration was contrary to that of ozone concentration, and the latter was significantly earlier than the former; ⑦ The variation of near surface ozone concentration could be affected by some meteorological factors, such as the relative humidity, wind speed, wind direction and sunshine duration, so ozone pollution was jointly affected by many factors.