For investigating the changes of sediment yield reduction by soil conservation with spatial scale,this study collected data of the areas implementing soil conservation measures and the amounts of sediment yield reduction associated with soil conservation measures for 64 catchments with different sizes in the middle Yellow River.The soil conservation measures in discussion include land terracing,tree and grass planting,land creating behind sediment-checking dams.Results show that the reduction of specific sediment yield due to implementation of soil conservation measures does not present a significant trend of increase or decrease with the increase of catchment size.