A small watershed is both the main source of regional sediment yield and the basic unit of erosion control and ecological environment restoration81. Table 1 shows runoff and sediment parameters and cluster results of different event-based rainstorms in Zhifanggou Watershed. The cluster results indicate that 17 rainstorms can be broadly divided into two major categories: (i) The first is the strongest rainstorm event, which reflects the maximum peak discharge, and the maximum suspended sediment discharge, such as the rainstorm that occurred on 26 July 2000. The average flow rate in this rainstorm was 8.9263 m3/s, the peak flow rate was 17.2954 m3/s and the total flow was 16774.84 m3. This shows that the great rainstorm produced large runoff and very intensive erosion, and the concentrated runoff is a dynamic condition for strong erosion of loess soil. (ii) The second is the rainstorm event which reflects the individual peak discharge and suspended sediment transport, which forms the other 16 rainstorm events. The second category can be subdivided into two smaller categories: one category is the rainstorm event with average flow >1.3 m3/s and suspended sediment amount >1300 t; the other category is the rainstorm event where the suspended sediments are <1000 t. The two small categories can also be subdivided into many small categories at the next level. Therefore, Cluster Analysis can be used to measure the similarity of different rainfall erosion events. Based on regression and Cluster Analyses in Figs 3–9 and Table 1, the criterion of relationships between sediment yield and runoff under typical rainstorm events in Zhifanggou Watershed can be statistically summarized as follows. For rainstorm events of sediment modulus >1000 t/km2, the power function of the sediment-runoff fitting effect is better than the logarithmic function. For rainstorm events of sediment modulus between 300–1000 t/km2, the logarithmic function of the sediment-runoff fitting effect is superior to the power function. For rainstorm events of sediment modulus <300 t/km2, linear associations are stronger. Therefore, classifying and describing the similar characteristics of runoff erosion in different rainstorm events can both provide important data support for soil conservation planning in a watershed, and provide a strong theoretical basis for establishing soil erosion prediction models. So, Cluster Analysis is a useful tool to evaluate characteristics of different rainstorm erosion events and to understand soil erosion and sediment transport processes.