To evaluate vibration fatigue life of SES flexible seal materials, medium size water-jet flagellator which can simulate the actual vibration of SES flexible seals was made and various types of the flexible seal materials were tested. CR or U on double mesh weave nylon, CR on special weave nylon and Thermo Plastic Polyester Elastomer showed good fatigue life among the tested materials. Then, Thermo Plastic Polyester Elastomer was chosen as SES flexible seals, in order to obtain the data of durability of bow seal for 30 ton SES test craft and to study the relationships between flagellation test and bow seal's vibration test, both tests were conducted. As the results of the tests, it was proved that the maximum acceleration of the lowest part of the bow seal went up to 70 g, the mean frequency of the seals was about 60 Hz, and also the effectiveness of the flagellation test as a accelerated fatigue life test of seal materials was made clear.