Taking Zhifanggou Watershed of 8.27 km2 in the loess hilly and gully region as the study area, the characteristics of runoff erosion and sediment yield based on 17 observed rainstorm events from 1997–2010 were statistically evaluated. The pulsed rainstorm is both the original driving force of slope soil erosion, and one of the most important factors influencing sediment transport processes. The main power of water erosion is rainfall and surface runoff, the amounts of runoff and erosion are closely related to rainfall intensity and rainfall amount. However, correlations of rainfall-runoff and rainfall-sediment during different rainstorms are often scattered and the correlation coefficients are often weak, due to effects of the infiltration-excess runoff and soil conservation measures in the loess hilly region. Runoff has a strong correlation with sediment yield. It can be expressed by simple exponential or linear equations. The sediment transport modulus can be quantitatively estimated by the corresponding runoff-sediment correlation under different rainstorm events. The response characteristic of sediment yield simulation is variable in different levels of pulsed runoff-erosion events. Affected by hyper-concentration flows, great changes have occurred in the interactions between flow and sediment concentration for different flood events. For rainstorm events of sediment modulus >1000 t/km2, the power function of the sediment-runoff fitting effect is stronger 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 relationships are stronger. This new overall understanding opens opportunities for decision-makers and managers to conserve soil based on observation data of rainstorm erosion in small watersheds.