Objective To investigate the densities and seasonality of Culex pipiens pallens in the vicinity of Beijing Capital International Airport during 2011 to 2014, and to provide a basic data for the control and prevention of mosquito-borne diseases. Methods Seven monitoring stations within 2 000 m around Beijing Capital International Airport were included in this study during 2011 to 2014. Carbon dioxide light traps were used to capture mosquitoes according to GB/T 23797-2009. Descriptive analysis was performed with mosquito monitoring data from 2011 to 2014 in surrounding areas of Beijing Capital International Airport. Results A total of 126 212 adult mosquitoes were captured within the 4 years of investigation. Culex pipiens pallens was the predominant mosquito species (accounting for 85.59% of all captured mosquitoes), followed by Cx. tritaeniorhynchus (13.95%), Anopheles sinensis (0.28%), Aedes albopictus (0.18%), and 1 Armigeres subalbatus. The annual average density indices of Cx. pipiens pallens in the 4 years were 35.87, 43.44, 15.67 and 36.88 mosquitoes per light-hour, respectively. There were significant differences on annual average density between 2012 and 2013(q=4.150, P < 0.01), between 2014 and 2013 (q=3.553, P < 0.05), respectively. The monthly average densities ranged from 0.29 to 113.34 mosquitoes per light-hour. The peak of adult Cx. pipiens pallens density appeared from June to August. The annual average density indices of mosquitoes ranged from 4.34 to 144.21 mosquitoes per light-hour in seven monitoring stations. The densities for Cx. pipiens pallens were the highest at the riverside, the second were in central Airport, and the third were in parts of northern Airport. There were significant differences on annual average density between the riverside and the other 6 monitoring stations (P < 0.01). Conclusion The density indices of Cx. pipiens pallens were high in surrounding areas of Beijing Capital International Airport. Culex pipiens pallens mainly inhabited outdoor environments such as riverside. The activity peak period of mosquitoes was between June to August. The surveillance of Cx. pipiens pallens should be enhanced.