According to observed data, the laws of runoff and sediment yield and the impact of precipitation variation on the sediment-reducing rate of comprehensive sediment capture in tributaries? in northwestern Shanxi province, of the Hekouzhen-Longmen reaches of the Yellow river are analyzed. The two main problems ? including the establishment of a runoff and sediment yield model and the improvement of the calculating method for sediment reduction due to precipitation variation, are emphatically discussed. The impact of less-than-normal precipitation on the sediment reduction caused by comprehensive sediment capture is analyzed too. The results may provide a scientific basis for the compressive sediment capture in the tributaries of the Yellow river in northwestern Shanxi provincet and can be used as an important reference for further research on water and sediment variation in middle reaches of the Yellow river.