In order to explore the large-scale long-term law of river channel evolution in the Inner Mongolia reach of the Yellow River, the Pugebu-Chahekou section was selected as a study area. The lateral migrations of the river channel and the changes in river width at 129 cross-sections monitored in different years were analyzed using 3S technology and RTK data on the basis of four groups of multi-spectral remote sensing image data during the period of 1995, 1999, 2006 and 2013. The results show that the interpreted river morphology results using the 3S technology agreed with the measured results. The average width of the river showed a tendency of shrinkage, although fluctuation existed. The river width of the main stream decreased by 32. 24 m on average from 1995 to 2013, with a change rate of -9%. Curve cutoff phenomena occurred more than once. The geological conditions, inflowing water and sediment conditions, and channel morphology are important factors affecting river channel evolution. The change rates of river width in the sandy riverbed sections ranged from -12% to -33%, which were greater than those in the bedrock riverbed sections. The apparent shrinkage of the Zhaojunfen cross-section was affected by the increase of the content of sand into the Yellow River from the Kubuqi Desert in the south and ten tributaries upstream.