Abstract:  For further studying the problems on the sediment movement in the stem stream and river net of lake region, river and lake relation change and flood routing of Yangtze River middle and lower reaches after the Three Gorges Project being completed, a Changjing River's flood prevention physical model is suggested to be built, together with developing mathematic model calculations and prototype measurement analysis. Several key technology problems related to the models are primary researched, e.g., numerical simulation techniques for unsteady flow in river net, physical model movablebed simulation techniques, etc.. Some problems, e.g., how to determine similarity criterions of suspened sediment in distrted model, sediment incipient velocities in natural rivers, and flow sediment laden scale, etc., are proposed. And routes to solve these problems are explored.