Abstract: Based on the satellite images for the west and south parts of the Bohai Bay in different periods, we summarized in this paper the great changes of shoreline in the past forty years. The length of the shoreline decreased slightly first and then increased during the period of 1984 and 2010. The shoreline extended seaward, and in some places, it might expand up to a maximum of more than 20 kilometers. The tidal flat was expanding from 1984 to 2000, and the growing rate in the south was faster than that in the west. The area of the Bohai Bay has been decreasing due to shoreline advancing. Almost all the shoreline of the Bohai Bay have turned into artificial except for some estuary shorelines since 2010. Tidal flat evolution has been studied from the viewpoints of sediment source, hydrodynamic change and human activities. The study showed that the shoreline and tidal flat evolution in the area was affected by both the natural environment and the human activities. The influence of human activities is obviously increasing with time.