Abstract: Abstract: Soil amendment agent plays important role in improving soil structure and enhancing crop growth. Sodium carboxyl methyl cellulose (CMC) is anion linear polymer cellulose ether，which is odorless, tasteless and nontoxic. It is regarded as an effective soil amendment agent because of its strong water absorption capacity. In this paper, a laboratory study was carried out to investigate the influence of sodium carboxyl methyl cellulose on soil aggregate structure and soil water movement in the soil columns by respectively adding 0, 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0 g CMC into each 1 000 g soil collected from Changwu agro-ecological experiment station in the loess plateau. The results indicated that water stable aggregate content increased from 3.36% to 15.05%, and the soil fractal dimension reduced from 2.53 to 2.37 with increasing CMC content. In the meantime, clay content reduced from 3.47% to 0.84%, silt content reduced from 86.19% to 61.27%, but sand content increased from 10.35% to 37.89%. Clay and silt contents were negatively correlated with soil fractal dimension, and sand content was positively correlated with soil fractal dimension. The influence of clay content was most significant on soil fractal dimension. The content of soil particle less than 0.1 mm reduced from 85.59% to 48.41%, but the content of soil particle between 0.1 and 0.2 mm, 0.2 and 0.3 mm, 0.3 and 0.4 mm, 0.4 and 0.5 mm, 0.5 and 0.6 mm increased from 9.53% to 22.56, 2.14% to 10.99%, 1.31% to 6.69%, 0.84% to 4.31%, 0.43% to 2.81% respectively, and the content of soil particle larger than 0.6 mm increased slightly. The relationship between water stable aggregate content, soil fractal dimension, clay content, silt content, sand content and CMC content followed quadratic function (R2≥0.95, P≤2.92×10-3). The relationship between clay content, silt content, sand content and soil fractal dimension followed linear function (R2≥0.95, P≤1.85×10-6). The soil infiltration capacity and the stable infiltration rate reduced with increasing CMC content. The cumulative infiltration volume reduced from 14.36 cm to 3.28 cm after 700 minutes. The stable infiltration rate reduced from 0.0150 to 0.0028 cm/min, and the relationship between stable infiltration rate and CMC content followed linear function (R2=0.96, P=2.99×10-6). Infiltration rate in Philip formula reduced from 0.46 to 0.13, the empirical coefficient K in Kostiakov formula reduced from 0.29 to 0.16, but the exponent increased from 0.41 to 0.53. Soil water retention capacity was enhanced with the increasing CMC content. The residual water content, saturated water content and coefficient associated with intake value in van Genuchten formula were increased, but the shape coefficient decreased with increasing CMC content. The residual water content increased from 0.12 to 0.14, saturated water content increased from 0.42 to 0.46, coefficient associated with intake value increased from 0.0031 to 0.0054 and shape coefficient reduced from 1.75 to 1.40. The results suggested that CMC can hinder water movement by reacting with water to form gel and then the smaller soil particles can be combined into the bigger soil aggregates. In conclusion，CMC additions agent could change soil structure and decrease soil infiltration capacity effectively. This study may provide valuble information for the application of CMC in soil improvement.