Management of soil erosion in sloping fields is one of the main tasks of water and soil conservation. In order to investigate infiltration and erosion characteristics of soil in sloping fields during rainfall process, infiltration and erosion of loamy loess soils with two ESP levels under different slopes were conducted using a rain simulator in laboratory. Exchangeable sodium percentage (ESP) of soils was 2.8 and 52.0 respectively, and soil slope was within the range of 5%～25%. The experimental data indicated that soil infiltration rate increased with decreasing ESP or increasing slope under the rainfall condition, and soil erodibility increased with increase of soil ESP or soil slope. Accumulative erosion linearly increased with accumulative rainfall amount under various ESP levels and land slopes, it also increased with increased slope angle. However, the increasing gradient of soil erosion against slope was much faster in high ESP soil than in low ESP soil with greater land slopes (>15%). The empirical formula of USLE calculated the slope factor well for low ESP soil, but poorly for high ESP soil. The WEPP model underestimated slope factor at great slope steepness for both ESP soils due to hill erosion.