Abstract: Abstract: This paper analyzed the effect of warping dams of different configuration ratios on reducing sediment and major factors contribution rate by mathematical statistics method and the investigation data in Dali River basin in middle of Yellow River. The investigation data showed land area of different type dams increased with time in Dali River basin, but presented obviously slow increasing in the near future. Warping dams reduced mean flood amount with 18.4 million m3 and sediment 12.9 million t during 1960－2002 annually, and the ratio of different type dams was 80.1%, 14.6%, 5.3%, respectively. The period of biggest reduction of sediment with 30.2% was 1990 s, and the responding ratio of different type warping dams was 1.84:2.37:5.79. The sediment decrement of large-scale soil-retaining dam was 5.5 times than that of medium dam, and was 15 times than that of small dams. The optimized proportion of distributions of warping dams for achieving continuous sediment reduction in the future in drainage basin was 1:3.0:7.0. The maximum amount of sediment reduction by different types of soil retaining dams correlated closely with flood season rainfall and 1-day maximum rainfall. Within the sediment reduction capability of warping dams, the amount of sediment reduction increased with rainfall intensity, presenting the characteristics of "the more sediment reduction with the more incoming sediment". Reducing sediment of the warping dams had a proportionality relationship with observed flood in different periods. Since 1990s, sediment reduction was about 0.23 t/m3 of unit cubic meter of flood discharge. Sediment reduction amount was about 0.19t/m3 per unit cubic meter of flood discharge during 1970s and 1980s, and the amount was about 0.23 t/m3 since 1990s. The warping dams reduced sediment increased with the value of 3 major factors. The contribution ratio of the factors was in the order: the flood amount ＞rain season rainfall ＞1-day maximum rainfall.