Abstract：Based on the high resolution stratigraphic sequence stratigraphy theory and the principles applicable to conditions as to when climate cycle and ascending and descending cycles of the base level and sea level are over the whole region, this paper carried out a comparative study with high precision and sedimentary environment analysis of 23 drill holes and 2 holocene sections within 46 km2 of the region of interest, and also made an in-depth investigation of the ecological environment for the ancestors living at the cross-lake bridge. The results show that the ancestors at 8000aBP cross-lake bridge lived in an environment almost identical with the current one in terms of its land features, vegetations, animals and climate, and the reason why the ancestors at the cross-lake bridge “disappeared” all of a sudden was that the ascent of the sea level caused the submergence of its site. The sea water didn’t withdraw until 3000aBP, so it was unlikely for the ancestors to move back, which has left the later generations an impression of “mystery”.