The time for the impoundment of the Three Gorges reservoir is very short, and the scour and aggradations of the river bed are in continuous adjustment, all of which make both the inadaptability between navigable base level and navigable condition and the contradiction between available data and determining method for design water level more remarkable. Based on the hydrological data of year 1981—2002 before the reservoir, the corrections of the design water level are calculated by time division, the design water level calculated according to the observed dada after reservoir is revised, and the design water level of part hydrographic stations at the middle Yangtze River are determined. This paper compares the variation of the design water level before and after the reservoir, and analyzes the course of change.