The influences of Xiaolangdi reservoir on the replenishment of the Yellow River estuary wetland were analyzed, and the changes before and after the operation of the reservoir on the landscape pattern of Yellow River Delta wetlands were detected using remote sensing. The results show that rainfall was an im-portant source for the wetland replenishment. As the rainfall was unevenly distributed each year in the study area, periods ecologically short of water often occurred. From May to July each year, lateral seepage from the Yellow River and rainfall infiltrations were overlapped, providing large amount of water supply to re-charge the wetlands. The water supply of lateral seepage showed great influences in about 2.5 km of the ri-parian buffer, but no obvious effect on the entire wetland. After the operation of the reservoir, the total area of the wetland increased slightly, specifically with areal reduction of 90.29 km² in natural wetland and areal increase of 150.11 km² in artificial wetlands. The coastal wetlands have experienced sea erosion generally. Overall, the area of the wetlands in the study area increased substantially and the salinization process has been restrained after the operation of the reservoir.