Abstract: Due to the influence of water conservancy projects, the water and sediment regulation of the Yellow River is usually carried out in a relatively short period of time, and a large amount of sediment and fresh water are transported to the adjacent areas off the Yellow River Estuary, which resulted in the most dramatic changes in hydrological characteristics and geomorphology. Based on a large number of measured data in 2020, the temporal and spatial distribution of temperature and salinity, and the evolution of submarine topography were analyzed in detail, and the influence of water and sediment of the Yellow River on salinity distribution and underwater topography were discussed. Results show that the water regulation of the Yellow River has greatly changed the salinity distribution. The salinity is higher in low flow period, and the distribution range of low salinity area is limited. During the period of high discharge, the salinity decreased significantly, and the water range in the low salinity area expanded significantly, which satisfied the flow demand of the estuary environment. The submerged delta has undergone significant deposition. The accretion trend occurred in the active submerged delta in 2019-2021, while the erosion appeared in the old Qingshuigou submerged delta, the Gudong littoral zone, and deeper offshore area. Runoff and sediment load have been playing dominant roles in accretion and erosion characteristics of the adjacent areas off the estuary.