Objective:To determine the density and distribution of flies in military camps in Yingxiu Town of Wenchuan County,and provide evidences for pertinent disinsection to reduce the incidence of food-borne infectious diseases. Methods: The densities of flies in camps of the Iron Army,Armed Police Forces and the Red Army were determined using trap glue boards. Sites of sampling were selected according to spacial representativeness and homogeneity. The numbers of flies caught on the boards were counted after a period of 8 h (from 8:00 AM-16:00 PM) in different climate conditions. Non-parameters test and paired Student t test were used for statistical analysis. Results: The densities of fly distribution were significantly different between the 3 camps. The flies concentrated in the kitchen areas,temporary restrooms,and garbage dumping grounds. More flies were found in the hot,sunshine weather than in the cool,cloudy weather. Insecticide chlordimeform was very effective in controlling the flies. Insecticide-resistance was not observed. Conclusion: The deteriorating environment around the camps is the major reason for the increased density of flies in the camps. The poor sanitation condition is also a reason for increase of flies. Selective spray of insecticides in these specific sites,like temporary restrooms and rabbish dumping grounds,can effectively reduce the density of flies in the tents; attention should be paid to avoid ecology deterioration caused by over disinsection.