[目的] 掌握常熟港蝇类本底情况。[方法] 对蝇类密度、种群分布、季节消长情况进行了调查。[结果] 发现常熟港有蝇类5科15属20种;绿蝇为优势种;7、8月为蝇类活动高峰期。[结论] 要控制蝇密度,必须开展卫生宣传教育,搞好环境卫生。 [Objective] To master the background of flies in Changshu. [Method] The flies density, population distribution and seasonal fluctuation were investigated. [Result] The results showed that there were 20 species of 15 genera and 5 families of flies in Changshu. The flies were the dominant species and the peak of flies activity in July and August. [Conclusion] To control the density of flies, publicity and health education must be carried out to improve the sanitation.