The exposed feldspathic sandstone region is one of the main source regions of coarse sandiment in the middle reach of Yellow River. Studying the change law of slope micro-topography under rainfall condition had great significance to guide vegetation construction and reduce coarse sandiment into Yellow River. In this study, taking Baojiagou watershed in feldspathic sandstone region as the research object, through hierarchical clustering method and linear regression method, we divided the types of rainfall and studied their effects on runoff and sediment yield, we also analyzed the change law of slope micro-topography under rainfall condition. The results showed that:(1) The natural rainfall in the research area could be divided into four types, the type Ⅰ was long-duration heavy rain, the type Ⅱ was long-duration moderate to heavy rain, the type type Ⅲ was short-duration heavy rain, and the type IV was short-duration light to moderate rain. (2) Parabolic function correlation were existed between the P of the type Ⅱ rainfall and soil loss amount. There was a polynomial function relationship between I₃₀ of the type Ⅱ rainfall and runoff depth. Polynomial function correlation were existed between the P of the type Ⅲ rainfall and runoff depth and soil loss amount. There was a certain functional relationship between the I₃₀ of the type IV rainfall and the sand content in the water flux. (3) During one rainstorm season, the average value of micro-topography slope grandiant of exposed bed rock slope increased from 22.76° to 23.09°, the rill density on the slope surface increased from 0 to 33.73 m/m². With the continuous development of microtopography of slope surface, which was beneficial to the occurrence of erosion, the runoff and sediment yield on the slope surface increased.