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, and the design topography information from the storage device. The controller determines an intermediate design topography positioned above the actual topography and below the final design topography. The controller generates a command signal to move the work implement based on the intermediate design topography. The intermediate design topography includes a plurality of intermediate design surfaces divided in the traveling direction of the work vehicle. Inclination angles of at least two of the intermediate design surfaces differ from each other.