The fluctuation of inlet flow in a water treatment plant can change the filtration rate abruptly and ultimately reduce the filtration performance by leaking the detained particles in filter media. The surface wave, occurring in the intake well by the fluctuation of inlet flow, reaches the filtration process in a very short time (about 10 minutes), which makes it impossible to control the filtration rate stably. In this study the authors evaluated the effect of daily flow-rate fluctuation on the performance of sand filtration process, and the dual media composition was proposed to improve the filtration performance. Comparative column tests were carried out for the various dual media, such as sand and anthracite compositions. From the results of column tests, dual media with the composition of sand 45 cm and anthracite 30 cm is more effective than the single media with sand in filtration process. In addition, irrespective of dual media composition, the managing ability to cope with that fluctuation tends to be weak at the end of allowable filtration duration time.