Objective To understand species, population density, and seasonality of flies in human dwellings and surroundings in China and provide the avenue for prevention and control of flies. Methods The surveillance data of flies by cage traps from 42 national surveillance sites were collected during 2006 and 2015. The species composition, density and seasonal and annual fluctuations of different speciesof flies in different habitats, and provinces were compared. Results Percentage of Chrysomya megacephala, Musca domestica, Lucilia sericata, and species of Sarcophagidae together was 75.54%; Density of C. megacephala was 2.23 flies per cage and was the highest. Its density in all 4 habitats were all highest of the monitored species; Musca domestica was the second and density was 1.64 flies per cage. Its density was higher in farm produce markets and outdoor of restaurant than in the other habitats. The third was 1.22 flies per cage of L. sericata and the density was higher in farm produce markets and in green belts. The fourth was 0.88 flies per cage of Sarcophagidae and its density in green belts was obviously higher than in other habitats. Overall, the density of flies was decreasing from 2006 to 2015, except that in 2010. The density of flies from green belts and farm produce markets was similar and higher than that in other two places monitored which was also similar. Density in most provinces was lower than 10.00 flies per cage. Hainan province was 74.22 and was the highest. There was a single peak in June-August during the seasonal fluctuation of total flies. The seasonal fluctuation of every predominant species in different habitats and in most of years was similar. Conclusion Chrysomya megacephala, M. domestica, L. sericata, and species of Sarcophagidae were the predominant fly species in human dwellings and surroundings in China. The density of flies generally decreased since 2006.But surveillance can't be underemphasized. More attentions should be paid on fly control in green belts and in farm produce markets, for density in those habitats was higher than in other habitats. The density peaked in June-August. So, it was important to control flies before the peak occurred.