Abstract: Based on collation of the flooding levels of the 11 storm surges since 1895 in the west coast of Bohai Bay, this paper verified and redefined the flooding levels with a probability of exceedance of 1 in 50, 100, 200... to 10000 years. Contributions of both wind set-up and wave to high water levels are quantitatively estimated as 50cm, respectively. Moreover, the various factors, including sealevel rise (starting from 2009 for every 10-yr-interval in 2009-2100: 3-31cm), land subsidence coincident with reclamation, net increase of flooding level stimulated by the sealevel rise (2020-2050: 7.5-30cm) and the mouth-channel effect (10cm) were discussed. Based on these parameters, the extreme flooding levels under probability of exceedance of 1 in 50 to 10000 years, respectively, were predicted until 2050 for every 10-yr-interval, and the leveling-correction affected by the subsidence was also discussed. We indicate the height of the existing seadike is capable to defense the storm surges of 1 in 50 to 100 years. However, based on the comprehensive factors discussed in this paper, it is suggested that the seadike should be reached to +4.8m in 2020 and +5.1m in 2030, respectively (both the State 85 Datum).