Abstract: Based on the precipitation, runoff and sediment data from the hydrological station, cluster analysis and sediment content-flow（SSC-Q） hysteresis curve are used to study the runoff and sand transport characteristics of different types of flood events in the Mihe River Basin of the northern earth and rock mountainous areas from the event scale, and reveal the relationship between various floods and sediments, the contribution of sand transport and the influence mechanism of soil and water conservation measures. The results show that（1） The 261 flood events in the Mihe River Basin from 1951 to 2021 could be divided into four categories: small, medium, large and extra-large, and the flood hysteresis curve type was mainly figure-8. With the increase in flood magnitude, the flood duration and runoff sand transport of flood events showed an increasing trend, the runoff, and sediment variability increased, and the proportion of the composite hysteresis curve gradually increased.（2） The frequency of large-scale and extra-large flood events was the lowest, but the contribution rate of sand transport was as high as 86.9%, which was the main type of flood in the northern earth-rock mountainous area, and dominated the soil erosion disaster in the Mihe River Basin, which needs to be paid attention to in the governance of the river basin.（3） Water and soil conservation measures and human activities have a greater impact on medium and small flood events, and the variability of the water-sediment relationship exceeds 10%. However, the impact on large-scale flood events is relatively small, and the variability of water-sediment relationship is only 1.2%.Through the rational allocation of water and soil conservation measures in the river basin, the relationship between water and sediment in local small and medium-sized flood events can be adjusted, so as to achieve the purpose of flood storage and sediment control. At the same time, it is urgent to continue to strengthen soil erosion and flood prevention and control measures for exceptionally heavy rainfall to avoid serious damage to the ecological environment of the northern earthy mountainous areas. The research findings serve as a theoretical and practical basis for the development of soil and water conservation in the region and the response to exceptionally heavy rainstorms and flood events.