Abstract: Abstract: Coal mining has caused large areas of arable land to collapse and accumulate water and these areas cannot be cultivated. Since these areasare located on banks of the Yellow River, using the sediment from the Yellow River as filling for mining subsidence land, which could not only dredge the Yellow River but also solve the problem of lack of filling materials. However, sediment form the Yellow River is sandy in texture with limited capacity to retain water and nutrients. Related researches showed that bulk density mainly affecting soil water characteristic. In order to study the relationship between the bulk density of sediments from the Yellow River and its water movement parameters and select the best bulk densityto fill mining subsidence land, an experiment was conducted in thelab with 8 different bulk densities under identical conditions. The saturated water content and saturated hydraulic conductivity of the Yellow River sediment were measured under different bulk densities. Using the Rosetta module built-in the HYDRUS-1D softwarebased on the model of Van Genuchtento simulatereciprocal of air entryvalue ? and experiencedparameter m, and meanwhile, generation of corresponding water characteristic curves under different bulk densities. Based on the analysis of measured values and simulated results, the empirical models between the bulk density of Yellow River sediment and saturated water content, saturated hydraulic conductivity and model parameters (?, m) were established, respectively. The correlation coefficients were all greater than 0.99(P<0.01), and the determination coefficients were all greater than 0.93, and the relative error between the measured and simulated value were all less than 10.77%. Results showed that thematric potential was 0 in saturated condition, and the sediment water characteristics of the Yellow River were mainly determined by porosity. The saturated water content and thesaturated hydraulic conductivity both tended to decrease with the increase of the bulk density of the Yellow River sediments. While ?b (bulk density)≥1.5g/cm3, the decreasing trend of saturated hydraulic conductivity becomes smooth with the increase of bulk density. Water characteristics of the Yellow River sediment were not only related to porosity, but also related to soil suction under the non-saturation state.The value of the reciprocal of air entryvalueαwas the lowest when ?b =1.5g/cm3, and water loss is the slowest, therefore, the Yellow River sediment holding capacity was the best under this bulk density. The simulation test of unsaturated hydraulic conductivity also obtained the best bulk density is 1.5g/cm3. The main mechanism of the unsaturated hydraulic conductivity was high as non-capillary porositywas in a higher rate, in the early stage of permeability and the sediment of the Yellow River showed rapid water loss with low soil suction. When the bulk densitywas greater than 1.5g/cm3, the macro-pore was difficult to continue to compress with the improvement of the compactness. Unsaturated hydraulic conductivitydecreases trend became slowly with the bulk density progressively increased. In conlusion, the capillary porosity was thebiggestwhen the bulk density of Yellow River sediment was1.5g/cm3, which was more conducive to the retention of effective soil moisture. Therefore, the water retention capability of the Yellow River sediment can be improved by proper mechanical compaction control till the bulk density was 1.5g/cm3 in the practice of filling mining subsidence land.