Abstract: The sediment distribution and the water thermohaline structure are closely related to the mixing of the stratifiedwater in the Bohai Strait. The mixing level of the water column in spring tides is stronger than that in neap tides, that makes significant spring-neap difference in water thermohaline structure from south to north and from the bottom to the surface. The vertical spread of the Yellow Sea water mass was larger in spring tide than in neap tide in the middle and lower water layers near the Laotieshan channel, influenced by the water mixing effect, and the water thermocline and halocline here are also more apparent in spring tide. From the North Huangcheng Island to the south, affected by fresh water of the Bohai Coastal Current, the water salinity decreases gradually, while the water temperature increases. The thermocline and halocline are both clear in the surface layer. The thickness of the thermocline and halocline in neap tide was larger than that in spring tide. In addition, the water turbidity in the middle and bottom layer was higher in spring tide than in neap tide. For the reason that the bottom suspended sediment is derived from the resuspension of the seabed sediment and the sediment grain size increased gradually from south to north, the bottom turbidity decreased gradually from south to north.