Based on statistical and hydrometric data,a study has been made of the check dam construction and its sediment-trapping effects.The area(Ac) of the land created by the sediment trapped by check dams is used as an index for soil and water conservation beneficial of check dam measures.It has been found that the rate at which Ac increases attained the maximum in the 1970s,and then decreased in the 1980s,and further decreased in the 1990s.The sediment reduction beneficial by check dams has been estimated using hydrological approach.The results show that sediment reduction beneficial increased rapidly in the 1970s,attaining the maximum in the late 1970s and early 1980s,and then declined.The yearly increment of Ac increased from the mid-1960s,attaining the maximum in the early 1970s,and then declined.Since the construction of check dams failed to be continued,the yearly increment of Ac showed a greatly decrease in the late 1970s and in the 1980s,and the sediment reduction beneficial of check dams declined due to the filling-up of most existing check dams.As a result,following a significant decrease in the 1970s and 1980s,the sediment yield of the Wudinghe River showed an increasing trend from 1986 to 1996,mainly because the check dam construction failed to be continued after the old ones were filled up.Hence,it is suggested that the construction of check dams should be strengthened for a sustainable sediment reduction beneficial,so that the reduction of sediment to the Yellow River could be sustained.