By using the convectional meteorological observation data in Nanjing during 1981-2015 and NCEP/NCAR reanalysis data, the major synoptic situation before and after Spring Festival over Nanjing and its effects on atmospheric environment were analyzed. Results show that:(1) during 1981-2015, there are 19 times of cold air processes and 27 times of precipitation processes occurring before Spring Festival and 21 times of cold air processes and 25 times of precipitation processes occurring during Spring Festival in Nanjing area. And all the precipitation processes lasted for two days. Before and during the Spring Festival, there are eight years found no cold air and precipitation processes. (2) The affecting cold air processes were mainly from the middle and the west areas. The cold air center before the Spring Festival was located in the west of Lake Baikal, while during the Spring Festival, the center moved to the south and its intensity strengthened slightly; the 500 hPa was distributed as two ridges and one trough, and Nanjing was located in the trough area, so the cold air behind the trough went down the south and influenced Nanjing unceasingly; under the effects of cold air, Nanjing was dominated by northerly winds and was located in the maximum tangential wind areas, moreover, the cold air was beneficial to the scavenging and diffusion of the pollutant. (3)During the precipitation processes, the cold and warm airflow intersected in Nanjing, and Nanjing was located in the saddle field of southern and northern airflow intersection, moreover, the high humidity and the location of wind convergence zone helped the occurrence of precipitation and further helped the scavenging and diffusion of the pollutant. (4) Nanjing was in the average pressure field of sea surface pressure, and the surface wind speed was small, which was not beneficial to the diffusion of pollutant; at the same time, the relative humidity over ground was moderate, which helped the moisture absorption of pollutant radius expand and further made the atmospheric pollutant concentration increase; form the temperature stratification, the temperature over 700-1 000 hPa over Nanjing was consistent, and this neutral layer had a certain effect on the upward diffusion of atmospheric pollutant; the above meteorological conditions are all beneficial to the increasing of atmospheric pollutant concentration. The stable synoptic situation during the Spring Festival would aggravate the occurrence of polluted weather.