Abstract: Two cores were collected at the submarine delta of the Changjiang River in 2006 and the radionuclide isotope of ¹³⁷Cs was measured. The ¹³⁷Cs curves of the two cores clearly show maximum peaks, which correspond to the highest fallout in 1963. Sub-maximum peaks, which may correspond to the fallout in 1959, exist as well in the ¹³⁷Cs profiles. The depths of the peaks suggest that the average deposition rate of the submarine delta of the Changjiang River ranges from 2.4 cm/a to 4.8 cm/a during 1959-1964, while the average rate changes from 1.4 cm/a to 1.8 cm/a during 1964-2006. It indicates that the deposition rate of the submarine delta decreased, as a rapid response to the dramatic reduction of the sediment discharge after the impoundment of the Three Gorges Reservoir. Even the decrease in the average depositon rate is different from place to place, the decrease is quite high. It suggests that the Changjiang River Delta is suffered from a change, and erosion occurs in some places in the submarine delta already.