This article researches the seasonal differences caused by wave dynamics impacting on the riverbed during the flood and dry seasons in the mouth bars of the Yangtze River estuary.Some perceptions are as follows:1)For the distribution curve of wave energy,during the dry season,wave energy is focused on the range of 4.0～7.0 s,waveform presents a narrow peak,while during the flood season,the energy concentrates in the 4.0～12.0 s,waveform appears broad or double peaks;2)Compared with the dry season,the long period waves occurring in the flood season are more frequent,and the proportion of energy to the overall increases significantly,the quantity reaches dozens of times;3)In the mouth bars,according to different periods,waves can be divided into 3 types,i.e.low-energy wave,high-energy wave and transitional wave.Low-energy waves almost unchange the riverbed in deep water while high-energy waves are completely reverse,but the influence of transitional waves on the mouth bar area is uncertain,and it in determined according to the change of the wave direction.