In the reservoirs eliminating danger and reinforcement engineering in severe soil erosion area of the Loess Plateau in southern Ningxia of China, the construction technique of "raising earth dam from upstream deposited mud" is generally adopted. And the distribution rule of deposit layers is very important to evaluate the stability of the dam foundation. In order to investigate the profile stratification and spatial distribution characteristics of the upstream silted soil, the ground penetrating radar (GPR) was used to detect the silted soil in front of Dashahe reservoir in Xiji County, Guyuan City. In the selected detection area of the silted soil in front of the dam, 10 survey lines were laid. First, the number of superimpositions for the best image effect of radar detection was determined, and then detection was carried out at 0.5 m intervals (a total of 794 detection points) on all test lines. At the same time, a 1.5 m deep trench was excavated to observe the profile of the silting layer. And soil samples were taken from different depth profiles for laboratory experiments of basic physical-mechanical properties. The results showed that the optimal number of superpositions of radar detection was 512. Radar spectrum showed that there were six obvious sedimentary bedding layers in the range of 0 to 2.5 m. In the depth range of 4 m to 9 m, there was a clear and continuous outline of the river-bed profile, and the sedimentary thickness of the silt on each survey line ranged from 3.7 m to 8.2 m. Obvious sandy silt-clay silt bedding could be observed at the depth of about 50 cm in the trench, which was consistent with the image analysis of GPR at this position. These findings could provide a basis for the settlement calculation and engineering treatment measures of the silting layer in front of the earth-filled dam.