During the 2018 flood season, the flood discharging to the downstream of the Yellow River totals 22.2 billion m3, and the desilting from Xiaolangdi Reservoir reaches to 466 million tons, the deposition of watercourses above Sunkou is 256.1 million tons, of which, 192 million tons in the channel above Huayuankou. This is the highest and the maximum year in quantity of water, sediment discharge and deposition of the lower reaches since the operation of Xiaolangdi Reservoir. However, the flood level of the same discharge in watercourses above Huayuankou which has the highest sediments during the desilting declines instead of increasing. This article analyzed the erosion and deposition and relevant characteristics, the changes of water level with the same discharge along cross sections at hydrologic stations as well as the changes of water level with the same discharge of water gauge at vulnerable spots during floods and sediment discharge in July by using sediment method and cross-section method. The outcomes show that a large amount of sediment occur in branch channels and marginal bank of watercourses above Huayuankou, after floods have passed, main channels seem more obvious with concentrated rivers, higher velocity and lower river level with the same discharge. After July floods, the river level of the same discharge along cross-section in the downstream of Yellow River rises slowly, which yet still remains below that at the beginning. During 2018 flood season, the flood discharge has been found no obvious reduction in watercourses of the downstream of Yellow River. [ABSTRACT FROM AUTHOR]