Understanding hillslope erosion processes is important for the development of physically-based erosion prediction models. However, quantitative information about the successive development of interrill–rill–ephemeral gully erosion on hillslopes is still rare. In this study, rare earth elements (REEs) were employed as tracers to monitor the successive development of different erosion processes on a hillslope. Ten different REE oxides were individually mixed with cultivated loessial soil from farmland on the Loess Plateau of China. The ten tagged soils were packed in ten layers into a flume (5 m in length, 1 m in width and 0.7 m in depth with a 20° gradient). Simulated rainfall events with natural rainstorm intensities of 60- and 90-mm h⁻¹ were conducted, and each rainfall intensity event contained three subevents that lasted for 135 mm rainfall depth for each subevent. The runoff and sediments for each test were collected at the outlet of the flume at 4.5-minute and 3-minute intervals, respectively. The flow velocity, flow depth and width and depth of the main channel were also synchronously measured. The results showed that the hillslope erosion went through five evolutionary stages: interrill erosion, rill development, stabilized rill, ephemeral gully development, and stabilized ephemeral gully. These stages were quantitatively identified according to the changing contribution rates of the interrill, rill and ephemeral gully areas. The channel width always developed faster than the depth at both the 60 mm h⁻¹ and 90 mm h⁻¹ rainfall intensities. The hydrological parameters could greatly explain the channel evolution and particle size changes. A larger flow power of 90 mm h⁻¹ intensified the channel morphology evolution in the early development stage. The friction coefficient finally remained steady and the W/D ratio eventually approached a stable value of approximately 2 in the stabilized ephemeral gully stage. Selective erosion occurred in the transportation processes were gradually weakened due to rapid increase of flow power and the overall detachment of the large clods in the channel, as manifested by particle size distribution in sediments approaching primary particle size distribution with time. This study is helpful for deeply understanding hillslope erosion processes, especially the successive evolution of interrill-rill-ephemeral gully.