Purpose The relations between rill morphology indicators and particle size selectivity by rainfall events were investigated, providing a new perspective on the mechanism of rill morphology indicators impacting on rill erosion processes. Materials and methods Indoor rainfall experiments were carried out with three-dimensional (3D) laser scanning technique for better monitoring the rill morphological indicators, using two types of soil collected from the north part and the south part of the Loess Plateau, respectively. Results and discussions The higher degree of headward erosion is occurred on loamy clay (LC) soil from the south part of the Loess Plateau with the higher total length (6.65 m) due to the higher clay content. Higher degree of side erosion is demonstrated on sandy loam (SL) soil from the north part of the Loess Plateau with the higher mean rill width (0.09 +/- 0.00 m) due to the higher sand content. The ratios of rill width to depth do not show significant differences on two types of soil with the average value greater than 1, indicating the relatively higher degree of side erosion than downward erosion on both soils. Silt fraction is selected with much higher efficiency than other fractions in two types of soil due to the dominant silt fractions in the primary soil. Rill width (W) is the most sensitive indicator to the particle size selectivity, as both the contents of clay, silt and fine particles and the enrichment ratio of silt show significantly (P < 0.05) positive correlations with W. While, the enrichment ratio of sand fraction shows significantly (P < 0.05) negative correlations with rill maximum depth and degree of contour line departure. Conclusions The differences of rill morphology indicators on two types of soil slope mainly depend on soil texture and the development processes of rills.