Objective To understand the species,density and seasonal fluctuation of mosquito vectors in rural areas of Hai'an City,and to provide reference for mosquito vectors and mosquito borne disease control. Methods The density of adult and larva were monitored by light trap method and spoon trap method respectively,and the monitoring data were analyzed by descriptive statistics. Results A total of 91546 adult mosquitoes were captured in 2016-2019,including Culex pipiens pallens,Culex quinquefasciatus and Anopheles sinensis,accounting for 47.27%,41.11% and 13.50% of the total mosquito catches,respectively.There were significant differences among different mosquito species(χ²＝342.55,P<0.001).The change of mosquito density in different years showed a fluctuating growth trend.The seasonal fluctuation curve showed that the peak of adult mosquito density was from July to August.In different environments,the density of residential area (under the eaves of human house) was the highest,followed by the field (near paddy field),and the density of hospital was the lowest,with the average density of 327.62,147.52 and 71.07 insects/(lamp·night).The average larval densities of Anopheles and Culex in paddy field and irrigation water were 10.08 and 14.35 (strips / 20 spoons),respectively. Conclusion The main mosquito vectors in Hai'an city are Culex pipiens pallens,Culex quinquefasciatus and Anopheles sinensis.The density of mosquitoes in residential areas is high,so it is necessary to strengthen mosquito control measures in the surrounding areas of residents to effectively reduce the mosquito density.