Based on experiment, observed in-situ data and results of the literature, the macroscopic dynamic reasons for change of back silting amount in the deepwater channel project at north passage of the Yangtze estuary are studied. The results show that: 1) Compared with the dry season, the long-period waves in the flood season increase significantly, the proportion of wave energy with the period range of 8.0s to higher in total wave energy increases from 3.2 % in the dry season to 40.6% in the flood season; 2) High-energy wave motion produces significant adverse effects on siltation in navigation channel at the north passage, it is closely related to the increase of back silting amount; 3) The current scouring capability in the north channel along the way increases after the channel depth dredged to 12.5 m, it is beneficial for the sediment in channel to move higher; 4) The quantity of own sediment exchange in the mouth bars of the Yangtze estuary is far more than that from upstream, flood is not the dominant macro power reason that causes significant change of back silting amount in the deepwater channel project at the north passage; 5) Wave is the dominant macro power reason that causes significant change of back silting amount in the deepwater channel project at the north passage, in the future “wave dissipation” should become one of the guiding principles that shall not be ignored in design research work of deposition reduction project of the deepwater channel project at the north passage and waterway regulation engineering at the south passage, the north channel and the north branch of the Yangtze estuary.