This article introduces applications of 3S, Geographical Information System (GIS), Global Position System (GPS) and Remote Sensing (RS), in river’s flood control. Take revising the Lower Yellow River’s 1:50 000 riverway topographic maps as an example, the author elaborates how to use 3S to update the existing maps. It has shown that update of maps based on 3S is short in work period, cheap in cost and simple in process. Moreover, the revised topographic maps are with high precision and they can meet the urgent data requirements of Yellow River’s flood control. It can also provide a strong data support for the construction of Digital Yellow River.