Abstract: The first phase of the marine reclamation land project for the equipment manufacturing base in the Caofeidian Industrial Zone, called shortly as Manufacture Phase I Project, began to construct in 2009 and the construction of sea reclamation was completed in 2010. In the construction. sand extracting at the sea and blow-filling way were applied for the land formation. The elevation of the blow-filled area was +4.5m (i.e. the lowest theoretical tidal level in Caofeidian). Due to the holistic nature of ocean form, the complex pattern of motion and the continuity of dynamic process, the role of ocean engineering can alter the ocean hydrodynamic state under the natural conditions and affect directly or indirectly the environmental elements such as topography, geomorphology, erosion and deposition state, material transport, seawater quality, sediment quality, habitat of benthic organisms, and so on. Therefore, the analysis and assessment of marine hydrodynamic environmental impact are crucial. Based on the MIKE21 model and by using 2-D tidal current basic equation and referring to the hydrological data measured in the study area over the years, the impact on the hydrodynamic enivronment in the sand extraction area (where a warehousing and logistics project will be located) before and after the reclamation construction in the Manufacture Phase I Project is simulated. Through the verification of the calculation results of the tidal current field and the calculations of the changes of the tidal current field in the sand extraction area, it is obtained that after the constructions of the sand extraction and blow filling at the sea in the Manufacture Phase I Project, the tidal flow velocity in the sand extraction area decreases, with the maximum reduction being about 0.16 m/s, while on the east and west sides of the sand extraction area there is an increase in tidal flow velocity, with the maximum increase being about 0.14 m/s. The areas where the change in flow velocity exceeds 0.005 m/s can be controlled within a 2.5 km range of the sand extraction area, which will have no significant impact on the overall hydrodynamic conditions in the area.