Abstract: PM_2.5 has been a major concern of the public due to its obvious effect of reducing visibility and endangering human health. Based on the hourly PM_2.5 monitoring data gathered around the clock at 24 monitoring sites in the Chang-Zhu-Tan metropolitan area, analysis was performed of variation of PM_2.5 pollution throughout 7 days before spring festival, 7 days of spring festival and 7 days after the festival in 2013, 2014 and 2015 to explore impacts of holiday activities, including tourism, on air quality. After excluding the effect of meteorological factors (e.g. daily precipitation >4 mm), holiday impacts were analyzed from the following three aspects, namely, difference in PM_2.5 pollution level, difference in daily variation of PM_2.5 concentrations, and spatial variation of the holiday effect. Results show that PM_2.5 concentration was 12 μg·m^-3 higher during the holiday period than during the days before and after the holiday, as a whole in the metropolitan area, and 41.5% lower during the 7 days after the holiday than during the holiday period, revealing an obvious "post-holiday effect". Strongly affected by holiday activities, like setting off fire-cracks and fireworks, PM_2.5 concentration soared dramatically during the early hours from 00:00 to 02:00 each day of the holiday period, peaking at 02:00 and being 47.6% higher than that during the non-holiday periods. The holiday effect varied spatially across the study area. In Changsha, being the destination of tourists during the holiday period, PM_2.5 concentration was 33.5% higher during the Spring Festival than during the non-holiday periods, demonstrating apparent impacts of travelling and tourism activities on air quality.