Abstract: Since entered into the Bohai Sea in 1855, the mouth of the Yellow river has shifted for a dozen times. The last two times of artificial diversion were happened in 1976 and 1996 respectively. Recently, two sedimentary cores have been taken from the Yellow River Delta, and the grain-size and ²¹⁰Pb systematically studied. The grain-size components show dramatic changes when the river mouth migrated in 1976 and 1996. The lower part of core A19 (14.0~24cm) was formed in a deltaic environment, while the upper part (0~14.0cm) formed in a coastal environment. The grain size variation at 14.0cm recorded the migration of river mouth in 1996. The lower part (15.5cm~bottom) of core A25 was formed in a coastal environment, while the upper part was formed in a deltaic environment, indicating the mouth migration in 1976. The 210-Pb curves were in a periodical or anti-decay pattern, matching well with the river mouth migrations.