A work vehicle control system includes an actual topography acquisition device, a storage device, and a controller. The actual topography acquisition device acquires actual topography information, which indicates an actual topography of a work target. The storage device stores design topography information, which indicates a final design topography that is a target topography of the work target. The controller acquires the actual topography information from the actual topography acquisition device. The controller acquires the design topography information from the storage device. When the actual topography positioned below the final design topography is sloped, the controller generates a command signal to move the work implement along a locus positioned below the final design topography and below the actual topography, and a sloped locus that is positioned below the final design topography and above the actual topography.