Abstract: Bottom sediments acquired from the three surveys in the southwest Bohai Bay were studied for the types of surficial sediments and their temporal and spatial distribution pattern. It is revealed that the surficial sediments in the studied area are mainly composed of sandy silt and clayey silt. They are fine in the northwest,and coarser in the southeast. As far as vertical distribution is concerned, they are fine in deep-water and coarser in shallow-water. Sorting of the sediments shows a similar pattern, i.e. being higher in shallow-water but lower in deep-water,or being higher in the southeast of the study area; The skewness of the sediments shows that the distribution of sediments is symmetrical or nearly symmetrical in the study area. Comparison of the mean size from the three times of survey indicates that the sediments were getting finer with time.