【Objective】Scientific use of sodium carboxymethyl cellulose(CMC)to achieve water conservation and salt control is of great significance for the improvement of coastal sandy saline-alkali soil. It is therefore important to clarify the influence of CMC on the water movement law of coastal soil sand by evaluating the effect of CMC concentration on soil hydraulic parameters.【Method】In this study, a one-dimensional vertical infiltration experiment was carried out to study the effects of different CMC application amounts(0, 0.1, 0.2, 0.4, 0.6 g·kg^-1)on the infiltration characteristics, water distribution, and soil hydraulic parameters. 【Result】The results showed that the final cumulative infiltration increased by 4.90%～15.17%, and the infiltration time to reach the preset wetting front depth increased by 61.90%～604.73% with the increase of CMC application. The adsorptivity S in the Philip infiltration model decreased from 0.685 cm·min^-0.5 to 0.256 cm·min^-0.5 and the parameter K_sS_f in the Green-Ampt model decreased from 0.633 cm²·min^-1 to 0.096 cm²·min^-1 with CMC application. The S and the average soil water diffusivity could be described by a quadratic polynomial and exponential function, respectively. Soil water content increased by 0.7%～3.7% because CMC enhanced the soil water holding capacity. Additionally, the retention water content θ_r, saturated water content θ_s, and air-entry α reciprocal were positively correlated with the amount of CMC, and inversely proportional to the saturated water conductivity K_s and shape coefficient n. CMC induced a moderate variation to K_s and α, and a minor variation to θ_r, θ_s, and n. 【Conclusion】This study can provide a valuable theoretical reference for rational use of CMC for the improvement of coastal saline-alkali soil.