[Objective] The micromorphology and erosion characteristics of the feldspathic sandstone under natural rainfall conditions were studied, in order to provide theoretical reference for understanding the mechanism of soil erosion in this region.[Methods] The exposed feldspathic sandstone slope was selected as the research object, and the field monitoring and 3D laser scanning technology were combined to analyze the dynamic changes of the number, shape and geometric characteristics of the rills during 13 rainfall events. The influence of rill micro-morphological change processes on slope runoff and sediment yield was analyzed.[Results] The total rainfall in the study area during the observation period was 267.40 mm, the total rainfall duration was 5 893 min, the total runoff was 294.05 L, and the total sediment was 111.34 kg. The contribution of rainfall to runoff and sediment followed the order of moderate rain>heavy rain>light rain. Moderate rain had the highest impact on slope erosion. After the erosion stopped, the overall morphology of the rill became more complicated, with a total length of 40.52 m, an average width of 4.31 cm, and an average depth of 1.22 cm. The development process of the rills on the slope surface during a single rainfall was as follows:splash erosion-sheet erosion-wide and shallow rills-continuous rill network-ditch wall collapse-channel stability, the rills tend to be narrow and deep.[Conclusion] The morphological indicators of the rills all present an obvious quadratic polynomial correlation, the ratio of rill width to depth and gully density have significant effects on sediment yield.