[Objective] The sediment transport path, sediment connectivity and its influencing factors in the small watershed under the condition of extreme rainstorm of the reservoir were explored in order to explore the causes for dam failure and provide basis for the channel flood control. [Methods] Qingshuigou and Shejiagou small watersheds with similar areas and different shapes were selected to investigate the sedimentation in the channel after the rainstorm event occurred in Zizhou County, Shaanxi Province, on 26th July, 2017. The channel was divided into dam-gully section and natural gully section. The area and the shape coefficient of the watersheds, channel gradient and the type and distribution of check dams were used as factors to analyze the differences in sediment connectivity of the channels between the two small watersheds. [Results] Under the extreme rainstorm, all the check dams in Qingshuigou and Shejiagou were opened. The sediment connectivity showed a strong growth trend from the upstream to the downstream in Qingshuigou watershed, while it increased initially and then decreased in Shejiagou watershed. The sediment connectivity of the Qingshuigou watershed was stronger than that of Shejiagou watershed. Additionally, the soil erosion in Qingshuigou watershed was also more serious than that in Shejiagou watershed. Parallel dam system and hybrid dam systems, as well as check dams with horizontal tubes, shafts and drains showed better flood control capacity. [Conclusion] The area, the shape coefficient of watershed and channel gradient all affect the connectivity of channel sediment, while the type and distribution of check dams are the major factors.