Soil water infiltration process of field mulched by different thickness of gravel-sand in northwestern arid area of Ningxia was studied by using one-dimensional vertical water infiltration method. This study selected the gravel-sand thickness as the impact factor, and set five levels of thickness (0, 6, 9, 12, and 15 cm). The variation laws of wetting front movement and infiltration amount were observed, the infiltration characteristics of each treatment were compared, and the infiltration process was simulated using model fitting in this study. The results indicated that gravel-sand mulching improved soil water infiltration capacity, soil wetting front distance and infiltration volume increased significantly. Compared with CK, the cumulative infiltration increased by 4.3%, 11.8%, 12.8% and 17.1% under gravel-sand thickness of 6, 9, 12 and 15 cm, respectively, and average infiltration rate increased by 25.8%, 38.7%, 50% and 62.9%, respectively. Meanwhile, gravel-sand mulching changed the soil water infiltration curve. As the increasing of the gravel-sand thickness, the initial infiltration rate grew rapidly, while the steady infiltration rate increased slowly. Compared with CK, the initial infiltration rate raised by 40%, 81%, 91% and 110% under gravel-sand thickness of 6, 9, 12 and 15 cm, respectively, and the steady infiltration rate increased by 15.3%, 17.9%, 20.5% and 25.6%, respectively. The Kostiakov model, Horton model and Philip model were used to simulate the soil infiltration process, and the results indicated that Horton model fit better (R2＞0.98) than the rest two models, and it was more suitable to analyze and predict the soil infiltration process under different thickness of gravel-sand mulching in the northwestern arid area.