Rainfall-induced instability of loess slopes is very common. Based on the governing equation for unsaturated seepage

a computational model of the seepage field of loess slope is established. The VG function and Gardner function are used to describe the soil-water characteristic curve and permeability function

respectively. The analytical solution of rainfall infiltration is derived by using traveling wave approximation and series expansion method. The validity of the analytical solution is demonstrated by fitting the model test data to the soil-water parameters using the numerical inversion method. By comparing and analyzing the distribution law of volumetric water content between the experimental value and the analytical solution under different working conditions

it is found that the test values of volumetric water content at shallow measurement points in the slope test model are closer to the analytical solution

and the peak volumetric water content reached during the downward movement of the wetting front is smaller compared to the analytical solution; the test value of volumetric water content of deep measurement points in the slope test model has some error with the analytical solution in the early stage

and the analytical solution of volumetric water content of deep measurement points grows faster in the early stage compared with the test value

which is mainly attributed to the hysteresis of wetting front in deeper soil layers.