[Objective] In order to investigate the rainstorms and floods process and the soil erosion caused by rainstorms in small watershed, it is urgent to carry out the investigation of rainstorms and floods process and soil and water conservation, so as to provide scientific support for the next soil and water conservation decision. [Methods] The flood marks were measured and investigated in Huangmi East Ditch and Liangjiazhuang West Ditch by field investigation method, and the flood peak discharge modulus was calculated to analyze the erosion damage caused by rainstorm flood to small watershed. [Results]① The rainfall lasted for a long time and was strong. The cumulative rainfall in Liangjiazhuang West Ditch Valley and Huangmi East Ditch Valley reached 1008.5mm and 613.6mm, respectively. According to the flood mark survey, the peak discharge modulus of Huangmi East Ditch and Liangjiazhuang West Ditch watershed are 10.80m3/s·km2 and 36.07m3/s·km2 respectively. Slope and soil and water conservation measures are the main factors affecting flood peak discharge. Larger slope will increase flood peak discharge, and perfect soil and water conservation measures can play an effective role in peak reduction. (3) The investigated small watershed is located in the upper reaches of 泜 river basin, which is the main runoff producing area of the rainstorm center and flood. The peak flood discharge modulus of the small watershed is larger than that of the downstream hydrology station. (4) The erosion situation of Liangjiazhuang West Ditch is more serious than that of Huangmi East Ditch, mainly because the area proportion of orchards, terraces and check dam in Huangmi East Ditch is larger than that of Huangmi West Ditch, the average slope of Huangmi East Ditch is smaller than that of Liangjiazhuang West Ditch, and the peak duration of rainfall at Liangjiazhuang rain measuring station is longer. [Conclusion] It is necessary and effective to implement soil and water conservation measures, and to further improve the construction of terrace and terrace valley. Good soil and water conservation measures can effectively reduce the occurrence of flood peak discharge and erosion phenomenon.