Abstract: In order to study the river regime evolution of the braided reach in Lower Yellow River after the operation of the Xiaolangdi Reservoir, the Landsat satellite remote sensing images of the braided reach in Lower Yellow River during the past 20 years from 2001 to 2020 are selected, and the edge extraction algorithm is used based on ARCGIS and ENVI software to extract water edge and correct the normalized differences. The water body index method（MNDWI） is used to extract the water body and analyze the characteristic indicators such as the water surface width of the river channel during the flood season, the position of the mainstream after the flood season, and the number of central banks after the flood season. The results show that:（1）After the operation of Xiaolangdi Reservoir, after 20 years of dredging adjustment, the river conditions in the braided reach in Lower Yellow River have been significantly improved during the flood season, and the mainstream has basically returned.（2）There is no obvious change in the river shape of this reach, and the width of the water surface increases and decreases with the amount of water during the flood season, and generally widens year by year. However, the width of the water surface of the Jiahetan-Gaocun section is relatively stable due to the control of the river channel improvement project.（3）Using the MNDWI method to intelligently extract the water body, it is found that the swing of the mainstream presents three rules:（1）The position of the mainstream is basically unchanged.（2） Mainstream position moves in the same direction.（3） Mainstream locations are migratory.（4） The number of the mid-channel beaches is negatively correlated with the water volume, generally decreasing year by year from 2001 to 2007, reaching a minimum of 13 in 2007, increasing year by year from 2007 to 2015, reaching a maximum of 58 in 2015, and decreasing year by year from 2015 to 2020, and at the same time, the location of the river-shaped abrupt change in the channel will also change. The adjustment of river regime will change the effectiveness of the river improvement project, and will also affect the production and life of the people in the beach area. Therefore, it is necessary to strengthen the monitoring of the river regime in the wandering section of the Lower Yellow River and pay enough attention to the changes of the heart beach to enhance the understanding of the law of river situation adjustment and the evolution of the heart beach in the Lower Yellow River.