In this paper a three-dimensional tidal current model has been used to examine variations of local fluid field due to establishment of a dam. By imputing ten tides-K1, O1, P1, Q1, M2, S2, N2, K2, Sa and Ssathrough the open boundary of the Bohai strait and adopting 5′×5′ horizontal resolution the whole fluid field of the Bohai Sea was first simulated. The computed harmonic constants of m1and M2tides at seventeen observational stations along the coast of the Bohai Sea matched the observed values rather well. Taking the calculated numerical results as open boundary conditions, the local fluid field in the Kendong Oil Field by means of 1′×1′ horizontal resolution was then investigated. In the course of calculation, fine grids were embedded in coarse grids so as to enhance the computational order. In addition, the latest water-depth data of the Huanghe Delta coast area were adopted, thus topographic changes because of silt sediment in that region wouldn't affect the computed results. In the end, by analyzing the relative changes of the fluid field before and after the dam was established, that the effect on the dynamic environment of the local sea area mainly concentrated on the adjacent positions north and south of the dam was suggested.