Abstract: Aiming at the improvement measures of time scale distortion in the sediment model test for the middle-lower reaches of the Yangtze River, by reviewing the previous related research findings, the causes of the time scale distortion and its adverse impacts on the similarity of flow and sediment movement in the sediment models are analyzed in this study, and some relevant improving measures or assumptions for eliminating or mitigating the time scale distortion of the sediment models are reviewed. Then, by means of the case study of the model tests on the Nanjing reach of the Yangtze River, based on the adjustments of the generalized mode of the model water and sediment process, the studies of the improvement measures of the time scale distortion are carried out in this paper. The analysis results show that it is feasible to carry out the sediment tests according to the daily average generalized mode in the model water and sediment process. It is expected to solve or improve the difficult problems on water shortage in the rising period and water drainage in the falling period caused by the time scale distortion in the sediment model (especially for the long reach model) tests.